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BTMETER · BTMETER 3-Phase True-RMS Power Clamp Multimeter with 9999 Counts, AC/DC Voltage & Amperage, KW/HP, Power Factor, KVA/VAR, Inrush Current & Temperature Test, Electrical Teste 580P
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A three phase power clamp meter with 9999 count true RMS measurement, a 43 mm jaw, a dual display that shows two quantities at once, and a function list running from AC and DC voltage and current through inrush, resistance, capacitance, diode, continuity and temperature to true power, horsepower, reactive and apparent power, power factor, phase angle, frequency, phase rotation and phase sequence. The breadth is the reason to consider it. The reason to hesitate is not the mislabelled unit in the first bullet, which is a typing error the rest of the listing corrects, but the complete absence of a measurement category rating on an instrument offered for commercial and industrial panels.
Reactive and apparent power share a label they should not
The first bullet lists true power, horsepower, reactive power (KVA), apparent power (KVA), power factor, phase angle, frequency and phase rotation. Two of those entries carry the same unit, and they should not.
Where current and voltage are not in step with one another, which is the normal condition anywhere there are motors, transformers or fluorescent ballasts, the power in the circuit splits into parts that have to be counted separately.
- Real power, in watts or kilowatts, is the part converted into shaft work, heat or light. It is what the meter on the wall charges for.
- Reactive power, in volt amperes reactive, is the part that flows into a magnetic field on one part of the cycle and back out of it on the next. It does no work, and it still occupies the cables and the transformer.
- Apparent power, in volt amperes, is simply measured volts multiplied by measured amps. It is what sizes a supply, a generator or a breaker.
The three are related by a right angled triangle: apparent power squared equals real power squared plus reactive power squared. Power factor is real power divided by apparent power, and phase angle is the angle at the corner of that triangle. An instrument that reads all four is describing the whole triangle rather than one side of it, which is genuinely useful on a motor circuit.
So the typographical slip matters less than it first appears. Two bullets further down, the selectable dual displays include KW+PF, KW+KVAR, KW+KVA and KVA with phase angle as separate options, which means the instrument distinguishes the quantities even where the bullet does not. The product name carries KVA/VAR correctly as well. Treat the first bullet as a proofreading failure, not a measurement one.
Clamp the live conductor, and the listing says so
The fourth bullet does something unusual. It sells the 43 mm jaw on its ability to take non contact readings around multiple wires, then immediately warns that accurate readings require separating the hot and neutral conductors and clamping the live line only.
Both halves cannot be true at the same time, and the second half is the one to follow. A clamp measures the net current enclosed by the jaw. Put the outgoing and returning conductors of the same circuit inside it and those currents very nearly cancel, leaving the instrument reading the difference. On a healthy circuit that difference is a few milliamps of leakage. On a faulty one it is the earth fault current, which is why leakage clamps exist and why they are built with far higher sensitivity than this.
What the wide jaw really buys is physical access. A 43 mm opening fits around cable that a slim jaw cannot reach, including bunched conductors in a crowded panel and the larger sizes feeding three phase plant. That is worth having. It is not permission to clamp a whole cable bundle. Our note on measuring current with a clamp meter covers the technique in more detail.
Counts are resolution, and nothing here is accuracy
True RMS and 9999 counts are both in the title, and they describe different things that buyers routinely merge into one impression of precision.
True RMS describes what the instrument does with the waveform. A meter that is not true RMS measures the average of a rectified signal and multiplies by a constant that is only correct for a clean sine wave. Feed it the chopped current drawn by a variable speed drive, a switching supply or a dimmer and the reading is wrong by a margin that depends on the shape of the distortion. A true RMS instrument computes the heating equivalent of the actual waveform, which is the figure that matters for cable and overload sizing. On a meter aimed at heating, ventilation and air conditioning work, where drives are now routine, it is close to essential. There is more on this in our explainer on true RMS measurement.
Counts describe the display. 9999 counts means four digits of reading before the meter changes range, so the smallest step on the screen is finer than it would be on a 4000 count instrument. Finer steps are not the same as closer to the truth. An accuracy specification states how far the reading may sit from the real value, usually as a percentage of reading plus a number of counts, and no such figure appears anywhere in these five bullets for any function.
A 43 mm jaw for panels, with no category printed
The third and fifth bullets place this instrument in commercial and industrial electrical testing and in heating, ventilation and air conditioning troubleshooting on single phase and three phase supplies. That is where the omission bites.
| Specification | Published in the listing |
|---|---|
| Counts | 9999 |
| Sensing | True RMS |
| Jaw opening | 43 mm |
| Systems covered | Single phase, three phase three wire, three phase four wire |
| Dual display pairs | A+Hz, V+Hz, A+V, KW+HP, KW+PF, KW+KVAR, KW+KVA, KVA with phase angle |
| Functions | AC and DC voltage and current, inrush, resistance, capacitance, diode, continuity, temperature, true power, horsepower, reactive and apparent power, power factor, phase angle, frequency, phase rotation and sequence |
| Display | Large, backlit |
| Warranty | 12 months |
| Measurement category rating | Not stated in the listing bullets |
| Maximum voltage | Not stated in the listing bullets |
| Current range | Not stated in the listing bullets |
| Accuracy, any function | Not stated in the listing bullets |
| Inrush capture method or trigger level | Not stated in the listing bullets |
| Temperature range and probe type | Not stated in the listing bullets |
| Power source | Not stated in the listing bullets |
A measurement category rating is not a quality badge. It states which part of an installation the instrument and its leads are built to survive, because the further upstream you go the more energy is available behind a fault and the larger the transient a meter has to withstand without flashing over. Panel work on a three phase supply is exactly the environment the categories were written for, and a buyer cannot judge suitability from a page that omits both the category and the maximum voltage. Our explainer on category ratings sets out what each level permits.
This is not the same as a contradiction. The figures are simply absent, and they are the two figures the stated application makes essential. Ask for them in writing before taking the instrument into a live board.
The electrician this suits, and the one it does not
If you already work on three phase plant and your current instrument reads amps and volts but not the power triangle, the function list here is the argument. Reading real power, apparent power, reactive power and power factor at the same time as current, plus sequence and rotation on the same tool, replaces two or three separate checks. The 43 mm jaw and the dual display are both aimed at that work rather than at a bench.
If your work is domestic or light commercial, most of this capability will stay unused and a straightforward true RMS clamp with a published category rating and published accuracy is the better instrument. And if you need measurements that someone else will act on, whether that is sizing correction capacitors or signing off a supply, the missing accuracy figures matter more than the breadth of the function list. See three phase clamp meters for instruments whose listings publish those numbers.
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Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.
Frequently Asked Questions
Is reactive power measured in KVA or in KVAR?
In KVAR. There are three power quantities in an alternating current circuit and they have three units. Real power, the part that does work and shows on the bill, is measured in watts or kilowatts. Reactive power, the part that flows into and back out of magnetic and electric fields without doing work, is measured in volt amperes reactive, or KVAR. Apparent power, the simple product of root mean square volts and root mean square amps, is measured in volt amperes, or KVA. The first bullet prints KVA after both reactive and apparent power, which is a typographical error rather than a measurement one, because the display options later in the listing include KW+KVAR and KW+KVA as separate selections.
Why does the listing tell you to clamp the live conductor only?
Because a clamp responds to the net current passing through the jaw. Enclose the line and the neutral of the same circuit together and the two currents are nearly equal and opposite, so the instrument reads the small difference between them rather than the load current. That difference is itself a useful measurement, which is what a leakage clamp is built to find, but it is not what you want when you are checking a compressor draw. The warning in the fourth bullet is correct and most listings in this category leave it out.
Can a coil sensor measure direct current?
A coil on its own cannot. A current transformer or a Rogowski coil produces an output only from a changing magnetic field, so a steady direct current generates nothing to measure. Clamp meters that read direct current use a Hall effect element in the jaw, which responds to the field itself rather than to its rate of change. The fourth bullet describes a high precision coil sensor and credits it with accurate direct current measurement, and the title claims AC and DC amperage, so the listing is loose about which element in the jaw is doing which job.
What does 9999 counts tell you?
It describes resolution, not accuracy. Counts are the highest number the display can reach before the meter has to change range, so a 9999 count instrument shows four significant digits and can display, for example, tenths of a volt all the way to 999.9 V. A 4000 count meter would have to jump to whole volts above 400. More counts mean finer steps on the screen. They say nothing about how close the reading sits to the true value, and no accuracy figure appears anywhere in these bullets.
What is phase rotation testing for?
Finding out which way a three phase motor will turn before you couple it to anything. The three supply phases arrive in a sequence, and reversing any two of them reverses the direction of rotation. A pump driven backwards moves very little, a compressor driven backwards can be damaged, and a conveyor driven backwards is obvious but late. Checking sequence used to need a separate instrument, so a clamp that reads rotation and sequence alongside power is one less thing to carry. The listing states it covers single phase, three phase three wire and three phase four wire systems.
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