Extech Clamp-on Meters in South Africa
A clamp-on meter measures the current in a live conductor without breaking the circuit. The hinged jaw encircles a single conductor and reads the magnetic field the current produces around it, so an electrician can take a load reading on an energised board in seconds without isolating anything, disconnecting a cable or fitting a shunt.
Ecotao Enterprises supplies the full Extech clamp meter range nationwide from Cape Town — from 30 A low-current mini clamps for leakage hunting through to 2000 A True RMS instruments for main incomers, including models with built-in infrared thermometers for locating hot joints.
How a clamp-on meter works
A clamp meter — also called a clamp-on ammeter or tong tester — is a current-measuring instrument whose sensing element is a split, hinged magnetic core rather than a pair of probes. Because current flowing in a conductor generates a proportional magnetic field around it, encircling that conductor with the core lets the instrument infer the current without any electrical connection to the circuit. That single design decision is why clamp meters are the standard tool for live load measurement: there is no need to isolate, no need to break the conductor, and no series burden added to the circuit.
Current transformer sensing (AC only)
The jaw forms the core of a transformer whose primary winding is the conductor itself. The alternating magnetic field induces a proportional current in a secondary winding inside the jaw, which the meter measures directly. This method is simple, accurate and needs no zeroing, but it only responds to a changing field — a steady DC current produces a static field that induces nothing. AC-only instruments such as the Extech MA440 and MA443 use this principle.
Hall effect sensing (AC and DC)
A Hall effect semiconductor sits in a narrow gap cut into the jaw core and produces a voltage proportional to the flux passing through it, whether that flux is alternating or steady. This is what allows a single instrument to read both AC and DC. The trade-off is that the sensor also responds to the earth's magnetic field and to nearby steelwork, so AC/DC models carry a zero adjustment that must be pressed with the jaw shut and clear of any conductor before a DC reading is taken.
Clamp one conductor, never the whole flex
This is the single most common measurement error. Live and neutral in a two-core flex carry equal and opposite currents, so their magnetic fields cancel almost exactly and the meter reads close to zero on a perfectly healthy appliance. On a fixed installation, clamp the individual core inside the distribution board. On a plug-connected appliance you cannot safely separate the conductors, so use an AC line splitter accessory such as the Extech 480172, which opens the flex out and presents a single-conductor loop for the jaw. The same cancellation effect, used deliberately, is how you measure earth leakage: clamp live and neutral together and any residual reading is current returning via the earth path.
How to choose a clamp meter: five decisions
Clamp meter selection comes down to five independent questions. Work through them in order — each one eliminates part of the range, and getting the first two right matters far more than the feature list.
1. Do you need to measure DC current?
This is the first fork because it determines the sensing technology and cannot be added later. AC-only instruments cover conventional mains distribution, motors, lighting and heating. You need an AC/DC model the moment direct current is involved — which in South Africa most commonly means solar photovoltaic strings, battery banks and hybrid inverter installations, plus telecoms DC plant, UPS battery strings, standby generator control circuits, traction systems and automotive electrical work. If there is any prospect of PV or battery work, choose AC/DC.
2. Is the load waveform clean, or distorted by electronics?
An average-responding meter measures the rectified average of the waveform and scales it by a fixed factor that is only correct for an undistorted sine wave. A True RMS meter computes the actual root-mean-square value and stays accurate regardless of shape. On non-linear loads — variable speed drives, LED and fluorescent lighting banks, switched-mode power supplies, UPS systems, inverters, electronic ballasts — an average-responding meter can under-read by 20 to 40 percent. That is enough to make a genuinely overloaded circuit look comfortably within rating. For plain resistive and motor loads an average-responding model such as the MA440 is perfectly adequate and costs less.
3. What is the largest conductor you will ever clamp?
Size the jaw from your worst case, not your typical case, because a jaw that will not close fully gives a low reading rather than an obvious failure — an error that is very easy to miss in the field. Jaw size and current range are related but independent specifications, so confirm both.
| Jaw opening | Typical conductor | Where you use it | Extech models |
|---|---|---|---|
| 18–23 mm | Up to 4/0 AWG | Control wiring, branch circuits, crowded panels, vehicle looms, telecoms racks | MA120, 380941, 380942, 380947, 380950 |
| 30–32 mm | Up to ~500 MCM | Sub-distribution, motor feeders, three-phase branch circuits, HVAC plant | MA63, MA440, MA443, MA445, EX655, EX623A |
| 43–52 mm | Up to 750 MCM | Main incomers, large motor supplies, busbar tails, transformer secondaries | EX820A, EX840A, MA1500, 380926 |
4. What measurement category (CAT rating) does the work demand?
The IEC 61010 measurement category describes how much transient energy an instrument can survive at a given point in the installation — the closer to the supply origin, the higher the available fault energy and the more severe the transients. CAT II covers plug-connected loads and final circuits. CAT III covers fixed distribution boards, sub-mains and three-phase motor feeders. CAT IV covers the origin of the installation: the incoming service, the meter box and outdoor overhead work. Choose a rating at or above the highest-energy point you will work on, and read the voltage figure alongside it — CAT III-600 V and CAT IV-600 V are not the same instrument. Most fixed-installation work in South Africa warrants at least CAT III-600 V; the EX820A and EX840A carry CAT IV-600 V.
5. Which diagnostic extras actually earn their place?
- Inrush / peak capture — samples fast enough to catch the six-to-tenfold surge a motor or transformer draws at start-up, which distinguishes a genuinely undersized breaker from an abnormal starting current. On the 380926, MA1500, EX655, EX820A and EX840A.
- Built-in infrared thermometer — lets you read the load and then immediately check the terminal temperature without swapping tools. A joint running hot relative to its neighbours is the classic early sign of a loose or corroded termination. On the EX820A, EX840A and EX623A.
- Non-contact voltage detector (NCV) — a live-circuit check built into the meter body, so the first-line safety test does not depend on carrying a separate pen.
- Low pass filter / VFC mode — strips high-frequency switching noise so the meter reads the fundamental motor current on a variable speed drive output rather than the carrier. On the EX655 and MA63.
- Dual thermocouple inputs (T1, T2, T1−T2) — reads the differential across a heat exchanger or coil directly, instead of taking two readings and subtracting them. On the EX623A.
- Low-current resolution — a 0.1 mA or microamp range turns a clamp meter into a leakage-hunting instrument. On the 380942 and EX655.
Extech clamp meter comparison
Every current Extech clamp meter Ecotao supplies, ordered by maximum current. Specifications are as published by Extech Instruments (Teledyne FLIR).
| Model | Max current | AC / DC | True RMS | Jaw opening | Stands out for |
|---|---|---|---|---|---|
| 380926 | 2000 A | AC + DC | Yes | 50 mm (2.0 in) | Highest range; 0.1 µA / 0.1 mV multimeter resolution |
| MA1500 | 1500 A | AC + DC | Yes | 52 mm (2.0 in) | Inrush capture and peak hold for motor starting |
| EX840A | 1000 A | AC + DC | Yes | 43 mm (1.7 in) | Built-in IR thermometer; CAT IV-600 V |
| EX820A | 1000 A | AC | Yes | 43 mm (1.7 in) | Built-in IR thermometer; CAT IV-600 V |
| EX623A | 600 A | AC + DC | Yes | 32 mm (1.25 in) | Dual thermocouples + IR + NCV; DC µA flame rod range |
| EX655 | 600 A | AC + DC | Yes | 30 mm (1.18 in) | 600 µA low-current range; low pass filter for VFDs |
| MA445 | 400 A | AC + DC | Yes | 30 mm (1.2 in) | Type K temperature plus DC current in one meter |
| MA443 | 400 A | AC | Yes | 30 mm (1.2 in) | True RMS accuracy on distorted AC loads |
| MA440 | 400 A | AC | No | 30 mm (1.2 in) | Value option for clean sine-wave AC work |
| 380947 | 400 A | AC + DC | Yes | 23 mm (0.9 in) | Mini body with full 400 A capability |
| MA120 | 200 A | AC + DC | No | 18 mm (0.7 in) | Smallest jaw; NCV in the clamp tip plus LED torch |
| 380941 | 200 A | AC + DC | No | 23 mm (0.9 in) | 10 mA resolution; 40-segment bargraph |
| 380950 | 80 A | AC + DC | Yes | 23 mm (0.9 in) | Extra-small jaw for very congested enclosures |
| MA63 | 60 A | AC + DC | Yes | 30 mm (1.2 in) | 6000 mA automotive range; VFC mode for HVAC |
| 380942 | 30 A | AC + DC | Yes | 23 mm (0.9 in) | 0.1 mA AC resolution for leakage and control circuits |
Prices are not published because they track the import rate. Email sales@ecotao.co.za with a model number and quantity for a current quotation.
Full-size AC/DC clamp meters
Standard-body clamp meters combining a full digital multimeter with a current jaw. These are the instruments for distribution boards, motor feeders and main incomers — where you need range headroom, a jaw that will actually close around the cable, and voltage, resistance and capacitance functions in the same tool.
Extech 380926
2000 A True RMS AC/DC Clamp Meter
The top of the Extech clamp range, built for the point in an installation where current is measured in thousands of amps — transformer secondaries, main incomers and large busbar tails. The 50 mm jaw takes conductors up to 750 MCM, and unusually for a high-current instrument it does not compromise on the low end: full multimeter functions resolve to 0.1 µA and 0.1 mV, so the same meter that reads a 1500 A incomer can also chase a microamp-level control signal. Duty cycle measurement suits pulse-driven and switching circuits, and a push-button DC zero cancels the residual offset that Hall effect sensing picks up from ambient magnetic fields.
- Current range2000 A AC/DC
- Jaw opening50 mm, to 750 MCM
- Resolution0.1 µA / 0.1 mV
- Key functionsTrue RMS, duty cycle, DC zero
Extech MA1500
1500 A True RMS AC/DC Clamp Meter + NCV
A high-capacity True RMS clamp built around motor and plant work. The inrush function is the reason to choose it: it samples fast enough to capture the surge a motor or transformer draws in the first fraction of a second at start-up, which is what you need to tell an undersized breaker apart from a bearing problem or a failing start capacitor. Peak hold and MIN/MAX record excursions while your attention is elsewhere, and relative mode zeroes out capacitance lead offset for accurate motor capacitor checks. The 52 mm jaw accepts conductors up to 500 MCM. Supplied with test leads, a Type K bead wire temperature probe, 9 V battery and carrying case.
- Current range1500 A AC/DC
- Jaw opening52 mm, to 500 MCM
- Voltage400 mV to 600 V AC/DC
- Key functionsInrush, peak hold, MIN/MAX, NCV
Extech EX655
600 A True RMS AC/DC Clamp Meter + NCV
The most versatile instrument in the range for general electrical and HVAC work, largely because of its measurement span: a 600 A jaw at one end and a 600 µA range at the other, which means one meter handles both a motor feeder and a leakage investigation. The low pass filter strips drive switching noise so you read the fundamental motor current on a VFD output rather than the carrier frequency, and inrush mode captures start-up surges. A 6000 count backlit LCD with a trending bargraph shows whether a reading is drifting, and the DC zero function keeps Hall effect offset in check. Practical touches include an LED worklight for dark plant rooms. Supplied with test leads, a general purpose bead wire temperature probe and three AAA batteries.
- Current range600 A AC/DC
- Low current600 µA AC, 0.1 µA res.
- Jaw opening30 mm, to 350 MCM
- Key functionsLow pass filter, inrush, NCV, worklight
Extech MA445
400 A True RMS AC/DC Clamp Meter + NCV
The fully-specified member of the MA440 series, and the one to choose if you want a single mid-range meter that does not need a companion tool. It adds DC current for automotive, battery and PV work and a Type K thermocouple input for contact temperature to the series' standard True RMS AC current, 750 V voltage, 40 MΩ resistance, capacitance and frequency functions. The built-in NCV detector means the live-circuit check happens with the meter already in your hand. Suited to contractors who move between domestic, commercial and light industrial work in a single day.
- Current range400 A AC/DC
- VoltageTo 750 V AC
- TemperatureType K thermocouple
- Key functionsTrue RMS, capacitance, NCV
Extech MA443
400 A True RMS AC Clamp Meter + NCV
The middle model of the MA440 series: True RMS accuracy on AC current without paying for the DC function you may never use. This is the right choice for commercial and building services work where the loads are electronic — LED lighting banks, electronic ballasts, switched-mode supplies, UPS circuits — but nothing runs on DC. Full multimeter capability comes with it: 600 V AC and DC voltage, 40 MΩ resistance, 100 µF capacitance, frequency to 1 MHz, diode and continuity, plus the series NCV detector. The 30 mm jaw handles conductors to 500 MCM.
- Current range400 A AC (True RMS)
- Voltage600 V AC / DC
- Jaw opening30 mm, to 500 MCM
- Key functionsFrequency to 1 MHz, capacitance, NCV
Extech MA440
400 A AC Clamp Meter + NCV
The entry point to the MA440 series: an average-responding AC clamp meter for work where the waveform is clean and True RMS is not worth paying for — resistive heating, direct-on-line motors, straightforward domestic and small commercial distribution. It carries the same multimeter set as its siblings, with 600 V AC and DC voltage, 40 MΩ resistance, 100 µF capacitance, frequency, diode and continuity, plus the built-in non-contact voltage detector and the 30 mm jaw. If any part of your work involves drives, inverters or LED lighting, step up to the MA443 instead.
- Current range400 A AC
- ResponseAverage responding
- Jaw opening30 mm, to 500 MCM
- Key functionsResistance, capacitance, NCV
Extech MA63
60 A True RMS AC/DC Clamp Meter + NCV
A manual-ranging AC/DC clamp meter aimed squarely at two awkward jobs. The 6000 mA range resolves the small currents found in automotive circuits — parasitic battery drain, sensor and injector supplies, glow plug and relay circuits — that a 400 A meter simply cannot see. The VFC (variable frequency control) mode filters drive switching noise so you can diagnose variable-frequency HVAC plant without the reading jumping around. Three current ranges, AC and DC voltage to 600 V, full overload protection, plus resistance, capacitance, frequency, diode and continuity, data hold, low battery indicator and auto power off. Supplied with test leads, carrying case and two AAA batteries.
- Current range60 A AC/DC (3 ranges)
- Low current6000 mA range
- Jaw opening30 mm, to 500 MCM
- Key functionsVFC mode, True RMS, NCV
Clamp meters with built-in infrared thermometers
Current and temperature are the two measurements that between them explain most electrical faults, and they are far more useful taken together than apart. A cable carrying its rated current is fine; the same cable carrying its rated current at a terminal running 30 °C above its neighbours has a loose or corroded joint. These models put a non-contact infrared thermometer with a laser pointer into the meter body, so the temperature check happens in the same movement as the load reading — no second instrument, no putting down the clamp.
Extech EX840A
1000 A Clamp Meter with IR Thermometer
The successor to the long-running EX840, and the most complete diagnostic clamp in the range. It combines 1000 A True RMS AC and DC current measurement with a built-in non-contact infrared thermometer and laser pointer for locating hot spots on motors, contactors and terminations. The 6000 count LCD is brightly backlit for dim plant rooms and switch rooms, and the double-moulded ergonomic housing is shaped for genuine one-handed operation — which matters when your other hand is holding a torch or a board cover. The 43 mm jaw takes conductors up to 750 MCM or two 500 MCM. Critically, it carries a CAT IV-600 V rating, so it is appropriate at the origin of the installation and not just downstream of it.
- Current range1000 A AC/DC True RMS
- Safety ratingCAT IV-600 V
- Jaw opening43 mm, to 750 MCM
- TemperatureBuilt-in IR + laser pointer
Extech EX820A
1000 A True RMS AC Clamp Meter with IR
The AC-only counterpart to the EX840A, and the sensible pick where DC current is genuinely not part of the job. It shares the same body, the same 43 mm jaw for conductors to 750 MCM or two 500 MCM, the same 6000 count backlit display and the same CAT IV-600 V safety rating, along with the built-in infrared thermometer and laser pointer for hot-spot location. With 1000 A True RMS measurement it handles the distorted waveforms of commercial and industrial electronic loads accurately. Well suited to electricians, electrical contractors and plant maintenance teams working on mains AC distribution.
- Current range1000 A AC True RMS
- Safety ratingCAT IV-600 V
- Jaw opening43 mm, to 750 MCM
- Display6000 count, backlit
Extech EX623A
600 A Dual Input Clamp Meter with IR Thermometer and NCV
The HVAC specialist of the range, and the direct replacement for the discontinued EX613 — with the range raised from 400 A to 600 A and an infrared thermometer added. Its defining feature is dual Type K thermocouple inputs giving T1, T2 and T1−T2 differential temperature, so you read the temperature rise across a coil, heat exchanger or duct directly rather than taking two readings and doing the arithmetic. The built-in IR thermometer with laser pointer covers non-contact hot-spot work, and an NCV detector handles the live-circuit check. A DC microamp range makes it the tool for flame rod current measurement on gas-fired HVAC plant, where a few microamps decide whether the flame sensor is working. Capacitance extends to 40 mF for motor start and run capacitors. Supplied with test leads, 9 V battery, Type K thermocouple, bead wire temperature probe and carrying case.
- Current range600 A AC/DC True RMS
- TemperatureDual Type K + IR
- Jaw opening32 mm (1.25 in)
- Key functionsDC µA flame rod, 40 mF capacitance, NCV
Mini clamp meters
Mini clamps exist for two reasons that turn out to be related. The first is physical access: a slim 18 to 23 mm jaw reaches into a densely packed distribution board, a control panel or a vehicle loom where a full-size instrument simply will not fit around a single core. The second is resolution: because the sensing core is scaled for tens rather than hundreds of amps, these meters resolve down to milliamps and even fractions of a milliamp, which makes them the right tool for control circuits, standby drain and earth leakage investigation.
Extech 380947
400 A True RMS AC/DC Mini Clamp Meter
A full 400 A of True RMS AC/DC capability in a mini body — the model to choose when the constraint is access rather than range. The 23 mm jaw reaches into small areas and takes conductors to 4/0 AWG, while 1 mA resolution and low-current sensitivity mean it does not lose usefulness at the bottom of its span. Frequency measurement to 10 kHz makes it suitable for drive and switching diagnostics as well as straight load readings. Used across plant maintenance, electrical, HVAC and telecoms work, and equally at home on marine, fleet and motorcycle electrical repairs.
- Current range400 A AC / 400 A DC
- Resolution1 mA AC
- Jaw opening23 mm, to 4/0 AWG
- Key functionsTrue RMS, frequency to 10 kHz
Extech MA120
200 A AC/DC Mini Clamp Meter + Voltage Detector
The narrowest jaw in the Extech clamp range at just 18 mm, which is what gets it into the places nothing else reaches — densely wired consumer units, control cabinets, junction boxes and vehicle looms up to 300 MCM cable. Two features make it a genuine one-hand tool: the non-contact AC voltage detector is built into the clamp tip itself, so you point the jaw at a conductor to check it is live before opening the jaw around it; and a white LED flashlight is built into the body for working inside dark enclosures. Measures 200 A AC to 100 mA resolution with 3% basic ACA accuracy, plus frequency to 1 kHz at 0.01 Hz resolution, on a 2000 count display with autoranging, data hold and auto power off.
- Current range200 A AC/DC
- Jaw opening18 mm, 300 MCM cable
- NCV detector120/240 VAC via clamp tip
- Key functionsLED flashlight, frequency to 1 kHz
Extech 380941
200 A AC/DC Mini Clamp Meter
A 200 A mini clamp that resolves to 10 mA on both AC and DC, which is fine enough to see small changes in a control or standby circuit that a coarser meter rounds away. Its distinguishing feature is a fast 40-segment bargraph running alongside the digital reading: the digits tell you the value, the bargraph tells you whether it is stable, drifting or oscillating — useful when a fault is intermittent and the number alone looks fine. One-touch auto zero handles DC offset, and voltage, resistance and frequency ranges cover general fault-finding. MIN/MAX, data hold and auto power off round it out. The 23 mm jaw suits branch circuits and control wiring.
- Current range200 A AC/DC
- Resolution10 mA AC/DC
- Jaw opening23 mm (0.9 in)
- Key functions40-segment bargraph, auto zero, MIN/MAX
Extech 380950
80 A Mini AC/DC Clamp Meter
Built around an extra-small diameter jaw for the situations where even a standard mini clamp cannot get around a single core — crowded distribution boards, packed control panels, engine bay looms and cramped switchgear. It gives up top-end range in exchange for that access, which is the right trade when the currents you are chasing are modest anyway. 1 mA resolution and low-current sensitivity keep it useful on control and instrumentation circuits. A practical choice for plant maintenance, electrical, HVAC and telecoms work, and for residential, automotive, fleet, marine and motorcycle electrical repair. Supplied with test leads, two 1.5 V AAA batteries and a carrying case.
- Current range80 A AC/DC
- Resolution1 mA
- Jaw opening23 mm, extra-small profile
- Supplied withTest leads, AAA batteries, case
Extech 380942
30 A True RMS AC/DC Mini Clamp Meter
A low-current specialist rather than a general-purpose meter, and the model to reach for when the problem is a current that is too small to see. Its 400 mA range resolves to 0.1 mA AC, which is the resolution you need to trace the residual leakage causing an earth leakage unit to trip intermittently — clamp live and neutral together and the imbalance you read is the current returning through earth. The same sensitivity finds standby drain, control circuit anomalies and small current variances that a 400 A instrument rounds to zero. CAT III rated with True RMS accuracy on the distorted waveforms typical of leakage paths. Supplied with test leads, two AA batteries, soft carrying case and user manual.
- Current range400 mA / 4 A / 30 A
- Resolution0.1 mA AC, 1 mA DC
- Jaw opening23 mm, to 4/0 AWG
- Safety ratingCAT III, True RMS
Accessory: Extech 480172 AC Line Splitter
A clamp meter cannot read a plug-connected appliance flex directly, because live and neutral cancel. The 480172 line splitter plugs in between the appliance and the socket, separates the conductors and presents a single-conductor loop for the jaw — typically with a ×1 and a ×10 loop so you can gain resolution on small loads by multiplying the reading. It turns any clamp meter in this range into a practical appliance load tester. Available on request — ask for it by model number when you enquire.
Discontinued models and their replacements
Three clamp meters previously listed on this page have been discontinued by Extech Instruments. They are documented here because they remain in service across South Africa and because the correct replacement is not always obvious from the model number. Ecotao can still advise on support, accessories and migration for all three — contact us with your existing model and application.
Extech EX613
400 A Dual Input AC/DC Clamp Meter + NCV
The EX613 was the HVAC dual-thermocouple clamp: True RMS current and voltage, T1/T2/T1−T2 differential temperature, a DC microamp range for flame rod measurement, 40,000 µF capacitance for motor capacitors, a built-in NCV detector and a 32 mm jaw for conductors to 500 MCM. The EX623A carries all of that forward and adds a built-in infrared thermometer with laser pointer while raising the current range to 600 A, so it is a direct functional upgrade with no capability lost.
Extech EX820
1000 A True RMS AC Clamp Meter with IR Thermometer
The EX820 introduced the built-in infrared thermometer to Extech's 1000 A AC clamp, with peak hold for inrush and transients, a 1.7 in (43 mm) jaw for conductors to 750 MCM or two 500 MCM, and full multimeter functions including AC/DC voltage, resistance, capacitance, frequency, diode, continuity and Type K thermometry. The EX820A retains the design and raises the safety rating to CAT IV-600 V with a brighter 6000 count backlit display.
Extech EX840
1000 A AC/DC True RMS Clamp/DMM + IR Thermometer
The EX840 was the AC/DC version of the EX820, adding direct current measurement to the same 1000 A body with its built-in infrared thermometer — the combination that made it a standard choice for plant maintenance where both AC distribution and DC systems were in scope. The EX840A is its direct successor, keeping the 43 mm jaw and IR thermometer while adding a CAT IV-600 V rating and a 6000 count backlit display.
Clamp meter applications in South Africa
Local installation conditions shape which clamp meter is the right one more than most buyers expect. Three features of the South African electrical landscape in particular push the selection toward AC/DC and True RMS instruments.
Solar PV and hybrid inverter installations
The rooftop PV and battery build-out that followed sustained load-shedding has made DC current measurement a routine part of ordinary electrical work rather than a specialist niche. String current verification, battery bank charge and discharge current, and combiner box balance checks all require an AC/DC clamp meter with a Hall effect jaw — an AC-only current transformer instrument will read zero on a healthy PV string. The inverter output side then demands True RMS, because inverter AC waveforms are synthesised and an average-responding meter mis-scales them. In practice this means a single installation needs both capabilities, which is why models like the EX655, MA445 and EX840A suit SA solar work particularly well. Remember to zero the meter with the jaw closed before each DC reading.
Standby generators and changeover systems
Standby generation is near-universal in South African commercial and industrial premises. Commissioning and maintaining these systems means measuring generator output current under load, checking phase balance across a changeover panel and capturing the inrush when the load transfers — which is where a meter with an inrush or peak hold function earns its cost, since transfer surges are exactly the transients that trip an otherwise correctly sized breaker. The DC side matters too: starter battery charging current and control circuit supplies are DC, so an AC/DC instrument covers both halves of the system. The MA1500 and 380926 have the range headroom for larger sets.
Compliance, CAT ratings and Certificates of Compliance
Electrical installation work in South Africa is governed by SANS 10142-1, the wiring code for low-voltage installations, under the Occupational Health and Safety Act and its Electrical Installation Regulations. A registered person issuing a Certificate of Compliance must verify the installation, and current measurement under load is part of establishing that circuits, protective devices and conductor sizing are correctly matched in service rather than only on paper. Instrument selection matters for safety as well as accuracy: choose a measurement category appropriate to where you are working, and note that supply-origin work — the meter box, the incoming service, outdoor overhead connections — falls in CAT IV, above the CAT III rating that covers distribution boards. The EX820A and EX840A are rated CAT IV-600 V. If you are unsure which category applies to a given task, ask us before you buy rather than after.
Motor-driven plant, mining and agriculture
Across the Western Cape's agricultural pumping and cold chain sector, and in mining and heavy industry more broadly, the dominant load is the three-phase induction motor. Clamp meters are the first-line diagnostic: comparing current across all three phases reveals winding faults and supply imbalance long before a motor fails, while a running current creeping upward over successive readings points to bearing wear or mechanical binding. Where motors run on variable speed drives — increasingly the norm for pump and fan energy savings — a low pass filter or VFC mode is essential, because without it the meter reads the drive's switching carrier rather than the fundamental motor current and the number is meaningless. The EX655 and MA63 both provide this filtering.
Clamp meter questions answered
What is a clamp meter and how does it work?
A clamp meter, also called a clamp-on ammeter or tong tester, measures the current flowing in a conductor without breaking the circuit. Its hinged jaw encircles a single conductor and senses the magnetic field that current produces around it. AC-only clamp meters use a current transformer, where the alternating field induces a proportional current in a winding inside the jaw. AC/DC clamp meters use a Hall effect sensor in a gap in the jaw core, which responds to steady as well as alternating fields and so can also read direct current. Because nothing has to be disconnected, a clamp meter lets you take a live current reading on an energised panel in seconds.
What is the difference between a True RMS and an average-responding clamp meter?
An average-responding clamp meter measures the rectified average of the waveform and multiplies by a fixed factor that is only correct for a clean sine wave. A True RMS clamp meter computes the actual root-mean-square value, so it stays accurate on distorted waveforms. This matters wherever electronics chop the current — variable speed drives, LED and fluorescent lighting banks, switched-mode power supplies, UPS systems and solar inverters. On such loads an average-responding meter can under-read by 20 to 40 percent, which is enough to make an overloaded circuit look healthy. For general resistive loads and straightforward AC distribution an average-responding model like the MA440 is adequate and costs less.
Do I need an AC/DC clamp meter or is AC only enough?
AC-only clamp meters cover conventional mains distribution, motors and lighting. You need an AC/DC clamp meter as soon as direct current is involved, which in South Africa most often means solar photovoltaic strings, battery banks and hybrid inverter installations, plus telecoms DC plant, UPS batteries, traction and automotive electrical work. AC/DC models use a Hall effect sensor and normally have a zero adjustment, because the sensor picks up the earth's magnetic field and nearby steel. Press zero with the jaw closed and away from any conductor before taking a DC reading.
How do I choose the right clamp meter jaw size?
The jaw has to close fully around one conductor, so pick the size from the largest cable you will ever clamp, not the average one. As a guide, an 18–23 mm jaw suits control wiring, branch circuits and vehicle looms; a 30–32 mm jaw handles most sub-distribution and motor feeders up to roughly 500 MCM; and a 43–52 mm jaw is needed for main incomers, large motor supplies and busbar tails up to 750 MCM. Jaw size and current range are related but not the same thing, so confirm both. A jaw that will not close completely gives a low reading rather than no reading at all, which makes the error easy to miss.
Why does my clamp meter read zero on a working appliance lead?
Because you have clamped the whole flex rather than a single conductor. Live and neutral carry equal and opposite currents, so their magnetic fields cancel and the meter correctly reads close to zero. You must clamp one conductor only. On a fixed installation that usually means clamping the single core inside the distribution board. On a plug-in appliance you cannot separate the conductors safely, so use a line splitter accessory such as the Extech 480172, which separates the flex and presents a single conductor loop for the jaw.
What is inrush current and why do I need a clamp meter that captures it?
Inrush is the brief surge drawn when a motor, transformer or capacitive load first energises, and it can reach six to ten times the running current for a fraction of a second. A normal averaged reading updates too slowly to see it. An inrush or peak hold function samples fast enough to capture the surge value, which tells you whether a breaker is nuisance tripping because it is genuinely undersized or because the starting current is abnormal. The Extech 380926, MA1500, EX655 and the EX820A and EX840A all offer inrush or peak capture.
What CAT rating do I need for a clamp meter in South Africa?
The IEC 61010 measurement category describes how much transient energy the instrument can survive at a given point in the installation. CAT II covers plug-connected loads and final circuits, CAT III covers fixed distribution boards, sub-mains and three-phase motor feeders, and CAT IV covers the supply origin — the incoming service, meter box and outdoor overhead work. Choose a rating at or above the category of the highest-energy point you will work on, and check the voltage figure alongside it. Most fixed installation work in South Africa should be done with at least a CAT III-600 V instrument; the Extech EX820A and EX840A are rated CAT IV-600 V.
Can a clamp meter measure earth leakage current?
A general purpose clamp meter usually cannot, because leakage is in the milliamp range while the meter is scaled for tens or hundreds of amps. You need either a dedicated leakage clamp or a high-resolution low-current model. The Extech 380942 resolves to 0.1 mA AC on its 400 mA range, and the EX655 has a 600 µA range, which makes both useful for chasing the residual current that causes an earth leakage unit to trip intermittently. The technique is to clamp live and neutral together: any imbalance between them is the current returning through earth.
Are the Extech EX613, EX820 and EX840 clamp meters still available?
No. All three have been discontinued by Extech and replaced by upgraded models. The EX613 400 A dual input clamp meter is replaced by the EX623A, which raises the range to 600 A and adds a built-in infrared thermometer. The EX820 is replaced by the EX820A and the EX840 by the EX840A; both successors add a CAT IV-600 V safety rating and a 6000 count backlit display. Ecotao can still supply support information and accessories for the legacy models and can advise on migrating to the current equivalent.
How do I get a price or check availability on an Extech clamp meter in South Africa?
Ecotao Enterprises supplies the Extech clamp meter range throughout South Africa from Cape Town. Prices are quoted per enquiry because they track the import rate. Email sales@ecotao.co.za with the model number and quantity, or phone the head office on +27 21 911 5835, Zak on 086 142 8716 or Zaid on 082 390 3989. If you are not sure which model fits your application, describe the load, the largest cable you need to clamp and whether DC is involved, and we will recommend a model.
Get a quote on an Extech clamp meter
Ecotao Enterprises has supplied test and measurement instrumentation to South African industry, engineering consultancies, agriculture and laboratories for over two decades, operating from Plattekloof in Cape Town with nationwide delivery. Tell us the load you need to measure, the largest conductor you need to clamp and whether DC is involved, and we will recommend the right model rather than the most expensive one.
Specifications are as published by Extech Instruments (Teledyne FLIR) and are subject to change by the manufacturer without notice. Model availability confirmed against the Extech product catalogue. Extech and FLIR are trademarks of Teledyne FLIR LLC.