A standard clamp meter averages, and a motor start is over before the average settles. Inrush capture holds the peak so you can see whether a compressor is drawing a normal surge or a locked-rotor fault. This page compares seven meters that publish an inrush function and explains what the number can and cannot tell you.
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The comparison covers clamp meters whose manufacturer listings publish an inrush current function. Products that appeared in the source set but did not state an inrush function were excluded, and the count in the heading reflects only the meters written about. Every specification in the table and the reviews is taken from the listing bullets supplied.
Inrush in the jaw, plus a display that shows volts and amps at the same time.
1000 A True RMS with a 100 ms inrush window and a clear AC-only warning.
A 600 A True RMS clamp with inrush, VFD and LoZ at the bottom of the range.
1000 A True RMS with a stated 10 A floor for the inrush function.
600 A True RMS with inrush, VFD and LoZ in a single listing.
The same family as the CM06 but with a 1000 A range for bigger motors.
No pick matches that combination yet. Try a wider budget or a different measurement.
| Pick | Max current | Inrush window | Inrush limits | VFD mode | LoZ mode | NCV | |
|---|---|---|---|---|---|---|---|
| P1 | Not stated | Not stated | Not stated | Not stated | Not stated | Yes, in the clamp jaw | View |
| P2 | 1000 A AC/DC | About 100 ms | AC current only | Yes | Yes | Yes | View |
| P3 | 600 A AC/DC | About 100 ms | AC only | Yes | Yes | Not stated | View |
| P5 | 1000 A AC/DC | About 100 ms | AC only, works well above 10 A | Yes | Yes | Yes | View |
| P6 | 600 A | Not stated | Not stated | Yes | Yes | Yes | View |
| P7 | 1000 A AC/DC | About 100 ms | Not stated | Yes | Yes | Not stated | View |
Cells show only what the manufacturer listing publishes. Where a listing is silent the cell reads Not stated rather than an estimate. P1 is included on the strength of its stated inrush function even though the listing does not publish the capture window or the maximum current.
Six decisions that separate a meter that will answer your question from one that will not.
A 600 A meter covers domestic compressors and small pumps. A 1000 A meter covers larger three phase motors. Buy the range your biggest job needs, because you cannot measure a surge you have clipped.
Only some listings publish a minimum current for the inrush function. P5 states it works well above 10 A. If your loads are smaller than that, the capture may not fire at all.
Inrush decays over a few cycles to a few hundred milliseconds. A window of about 100 ms, as published on P2, P3, P5 and P7, catches the peak on most motors without holding a stale value.
Several listings state plainly that inrush works on AC current only. If you need to capture a DC motor start, none of these meters will do it through the inrush mode.
VFD filtering keeps readings sane on drive outputs. LoZ collapses ghost voltages so you can tell a real live conductor from an induced one. If you work in modern plant rooms, both are worth having.
None of these listings publish an accuracy figure for the inrush capture. Use the number to compare a suspect motor against a known good one, not as a calibrated measurement.
A standard clamp meter samples and averages over a period long enough to give a stable reading. Motor inrush is a short surge that decays within a few hundred milliseconds. By the time the average settles, the surge is over and the display shows the running current. Inrush mode holds the peak instead of averaging it.
It is the length of the capture window. The meter watches the current for about 100 ms after you trigger the function and holds the highest value it sees. That is long enough to catch the peak on most single phase compressors and small three phase motors, and short enough that the meter is not still holding a value after the motor has settled.
Not according to the listings. P2 states plainly that the inrush function cannot test DC current and is only available in AC. P5 and P3 say the same. If you need to characterise a DC motor start, you need a different approach.
None of the listings publish an accuracy figure for the inrush capture, so treat the number as a diagnostic comparison rather than a calibrated measurement. Use it to see whether a suspect motor draws more surge than a known good one, and to confirm that a start is not a locked rotor event.
Inrush mode captures a peak over a short window at start. VFD mode filters the high frequency switching content of a variable frequency drive output so the meter reports a meaningful current or voltage. They solve different problems and you will use them on different equipment.
Usually not. A 600 A meter covers domestic compressors, furnace blowers and small pumps, and the 600 A models here include the same inrush, VFD and LoZ functions as the larger ones. The 1000 A range only matters when you move up to larger three phase motors.
The CL445 puts the inrush function where it belongs for service work: in the clamp jaw. That matters because a motor start is a magnetic event, and the jaw reads the magnetic field around the conductor without you breaking the circuit. The listing also separates the measurement paths cleanly. Current, inrush and non-contact voltage come from the jaw; voltage, resistance, continuity, frequency, duty cycle, DC microamps, diode and capacitance come from the leads; temperature comes from a thermocouple. That split tells you the meter is built for a technician who is already holding two things at once.
The dual voltage and current display is the feature that changes how you work. When you are chasing a compressor that trips on start, you want to know the supply voltage at the moment the contactor pulls in, not five seconds later. Seeing both numbers on one backlit screen means you are not cycling the dial between readings while the machine is running.
DC microamps is the quiet inclusion here. Flame rectification circuits on gas-fired equipment are measured in microamps, and a clamp meter that reads them saves carrying a second instrument. The listing does not publish an inrush capture window, so treat the function as present but unspecified in duration. For everything the listing does state, this is the most complete package for HVAC work.
The AstroAI listing is unusually honest about the limits of its inrush function. It states the measuring time is about 100 ms and then adds a note that inrush cannot test DC current and is only available in AC. That note is the single most useful sentence on the page, because a buyer who assumes inrush works on a DC motor will be disappointed. Read it before you buy.
The 100 ms window is the mechanism worth understanding. Motor inrush decays over a few cycles to a few hundred milliseconds depending on the motor and load. A capture window of about 100 ms sits inside that decay, which is long enough to catch the peak on most single phase compressors and small three phase motors, and short enough that the meter is not still holding a value after the motor has settled. The listing does not publish a minimum current for the function to trigger, so on very small loads the reading may be unreliable.
VFD and LoZ modes round the meter out. VFD filtering matters because a drive output is a switching waveform, and a meter without filtering will report a number that is neither the fundamental nor the true RMS. LoZ mode loads the circuit slightly to collapse induced ghost voltages, which is how you tell a real live conductor from a capacitively coupled reading. For the position it occupies, this is a lot of stated capability.
The CM06 is the 600 A member of a family of listings that share almost identical wording. The listing describes it as a feature-rich entry-level clamp multimeter aimed at automotive electrical testing and household electrical work. That framing is accurate: 600 A covers domestic compressors, small pumps, furnace blowers and most automotive starting circuits, and the True RMS front end means the reading is meaningful on the distorted waveforms those loads produce.
The inrush function carries the same 100 ms note as the larger meters, and the same AC-only restriction. The listing does not publish a minimum current for the function, which is the number that would tell you whether it will trigger on a fridge compressor drawing a modest surge. If your work is mostly small single phase loads, that omission is worth knowing about before you commit.
VFD and LoZ modes are present, which is more than the price position would suggest. The VFD filter is the one that matters if you ever put the jaw around a drive output; without it the reading drifts with the switching frequency. LoZ is the ghost voltage check. Neither mode is a substitute for a proper drive analyser, but both make the meter usable in a modern plant room rather than only on fixed speed equipment.
The HT208D listing does something the others do not: it publishes a minimum current for the inrush function. The text says that when the current is greater than 10 A the inrush function works well. That single figure tells you more about the instrument than any accuracy claim, because it defines the loads the meter is built for. A 10 A floor means it is aimed at motors and compressors, not at small electronics or control circuits.
The rest of the specification is the familiar 1000 A AC/DC, 1000 V AC/DC, True RMS package with frequency, duty cycle, resistance, capacitance, diode, continuity and temperature. The listing frames it for labs, factories and households, which is broad, but the 10 A inrush floor narrows the real use case to equipment with a genuine starting surge.
Non-contact voltage and a flashlight are the practical additions. NCV lets you confirm a conductor is live before you put the jaw around it, and the flashlight matters more than it sounds when you are working in a panel with the door open and the room lights behind you. The listing does not publish an accuracy figure for the inrush capture itself, so treat the number as a comparative diagnostic rather than a calibrated measurement.
The CM87C is a 600 A True RMS clamp with the full function list: AC and DC current and voltage, inrush, capacitance, resistance, continuity, diode, frequency and temperature, plus non-contact voltage and live wire detection. The listing describes the inrush function as measuring the maximum current at the moment the machine is started, which is the correct description of what a peak-hold inrush mode does.
The 600 A ceiling is the deciding constraint. On a domestic air conditioner, a fridge compressor or a furnace blower, 600 A is generous. On a large three phase motor it is not, and you would need one of the 1000 A meters instead. The listing does not publish the inrush capture window, so unlike the AstroAI and KAIWEETS entries you cannot compare the window directly.
VFD and LoZ modes are both present and described in the same terms as the rest of this family. The listing claims higher accuracy readings from both modes, which is a reasonable description of what filtering and low impedance input do, though no accuracy figures are published to support the word higher. The backlit display, flashlight, data hold, low battery indicator and auto shut-off are the expected conveniences. For a 600 A meter this is a complete package.
The CM06Pro is the 1000 A member of the POROMETISTO family. The listing describes it as a professional clamp meter for HVAC and industrial motor testing, and the 1000 A range is what earns that description. Where the CM06 stops at 600 A, this one covers larger three phase motors and the higher starting surges that come with them.
The inrush function is stated at approximately 100 ms and the listing ties it explicitly to motors and compressor circuits. That is the correct application. The listing does not publish a minimum trigger current, so the same caveat applies as to the CM06: on small loads the capture may not fire reliably.
VFD and LoZ modes are present and described in the same terms as the rest of the family. The listing claims reliable results in electrically noisy environments, which is what the VFD filter is for. No accuracy figures are published for either mode, and the inrush accuracy is likewise unstated. The function list covers capacitance, frequency, resistance and temperature alongside the current and voltage ranges. If you need the 1000 A headroom and want the same operating logic as the CM06, this is the direct step up.
Short answer: For most HVAC and motor work, P1 is the pick because the listing puts the inrush function in the clamp jaw alongside non-contact voltage and a dual voltage and current display, so you can watch the running value while you capture the start. P5 and P9 are the same meter under two listings and both publish a 1000 A AC/DC range with a 100 ms inrush window that the listing says works above 10 A, which suits larger single and three phase motors. P2 is the value option: 1000 A, True RMS, VFD and LoZ modes, and an inrush function the listing explicitly restricts to AC. If you only work on domestic compressors and small pumps, P3, P6 and P12 publish a 600 A range that covers them, and P7 is the 1000 A version of the same family.
A clamp meter works by measuring the magnetic field around a conductor. The jaw does not touch the wire, so there is no circuit to break and no burden voltage to disturb the load. That part is straightforward. The complication is what the meter does with the field it senses.
A general purpose clamp meter samples the field and averages it over a window chosen to give a stable display. That is exactly what you want when you are reading a steady running current. It is exactly what you do not want when the event you care about lasts a fraction of a second. A motor start produces a surge that rises almost instantly and then decays over a few cycles to a few hundred milliseconds. An averaging meter started before the motor and read after it will show you the running current and nothing else. The surge happened between two averages and left no trace on the display.
Inrush mode changes the sampling strategy. Instead of averaging, the meter watches for a peak over a short defined window and holds the highest value it sees. The window is the specification that matters, and it is the one most listings leave out. Where it is published, it is about 100 ms. That figure is not arbitrary. It is long enough to sit inside the decay of a typical motor start and short enough that the meter is not still holding a value after the motor has reached running speed. If you want the broader picture of what these instruments do outside the inrush function, the general clamp meter comparison covers the category.
The inrush figure is a diagnostic, not a specification. A healthy motor draws a predictable surge on start, typically several times its running current, and then settles. When the surge is wrong, the shape of the wrongness points at the fault.
A surge that is far higher than expected, or one that does not decay, suggests the rotor is not turning freely. That is the locked rotor case, and it is the one that trips breakers and burns windings. A surge that is lower than expected can point at a supply problem, a failing capacitor on a single phase motor, or a start winding that is not being energised. A surge that is normal but followed by a running current that is too high points somewhere else entirely, often at a mechanical load or a failing bearing.
The reason to measure rather than guess is that the breaker trip curve and the motor protection are both sized around the start. If you only ever read running current, you are blind to the part of the cycle that actually stresses the protection. The listing for P5 is unusually useful here because it publishes a floor: the inrush function works well above 10 A. That tells you the meter is built for loads with a real surge, not for control circuits. For work on drive-fed motors specifically, the VFD clamp meter comparison goes into the filtering question in more detail.
Read the listings on this page and a pattern emerges. Almost every meter claims True RMS, a count resolution, a maximum current and a list of functions. Very few publish the two numbers that decide whether the inrush function will actually work for you: the capture window and the minimum current at which the function triggers.
P2, P3, P5 and P7 publish the window as about 100 ms. P5 goes further and publishes the trigger floor. The others are silent. That silence is not necessarily a defect, but it means you cannot compare them on the specification that matters, and you should not assume they behave the same way. A meter with an unstated window might capture 20 ms or 500 ms; the first would miss a slow start, the second would hold a value that no longer reflects the surge.
The same logic applies to accuracy. None of these listings publish an accuracy figure for the inrush capture itself. That is normal for the category, and it is why the honest use of the function is comparative. Measure a motor you know is healthy, record the number, and then measure the suspect one. The difference between the two readings is the information. An absolute figure quoted to three digits would imply a precision the listing does not claim.
A clamp meter has no moving parts in the measurement path, which makes it feel maintenance free. The jaw is the exception. The mating faces of the jaw are part of the magnetic circuit, and anything that separates them changes the reading. Dust, paint, metal filings and a film of oil all introduce an air gap, and an air gap reduces the sensed field. A meter that reads low on every circuit is often a meter with dirty jaw faces.
The fix is simple: wipe the mating faces with a clean cloth and check that they close flush with no visible gap. Do this before you trust a low reading, and especially before you conclude that a motor is drawing less than it should.
The other maintenance item is the battery. Inrush mode is a peak capture, and a weak battery can cause the capture to behave erratically before the low battery indicator becomes obvious. If a reading looks wrong and the jaw is clean, replace the battery before you chase a fault that is not there. The test leads deserve the same attention: a cracked lead or a loose connector will affect every voltage reading, and the clamp jaw will tell you nothing about it.
An inrush clamp meter answers one question well: how much current did this load draw at the moment it started. It is a diagnostic instrument, and it is not an alarm, a recorder or a power quality analyser.
It is not an alarm. None of these meters will warn you that a motor is about to fail. They show a number when you are standing in front of the equipment. If you need continuous protection, that is a job for a motor protection relay or a thermal overload, not a handheld meter.
It is not a recorder. The capture window is about 100 ms on the meters that publish it. You get one number per start, not a waveform. If you need to see the shape of the surge, you need a recording instrument with a current probe, which is a different class of tool.
It is not a power quality analyser. True RMS tells you the heating equivalent of a distorted waveform, which is the right number for a motor. It does not tell you the harmonic content, the phase relationship or the power factor. For drive work, the filtering question is covered in the VFD measurement guide, and for DC motor checks the approach is different again, as set out in the DC motor clamp meter comparison. Knowing where a tool stops is as useful as knowing what it does.
The comparison covers clamp meters whose manufacturer listings publish an inrush current function. Products that appeared in the source set but did not state an inrush function were excluded, and the count in the heading reflects only the meters written about. Every specification in the table and the reviews is taken from the listing bullets supplied. Where a listing does not publish a figure, the text says so rather than estimating. P5 and P9 are the same meter under two listings with near identical wording; P9 was excluded to avoid duplicating a pick, and the same reasoning applied to P4, P8, P10, P11 and P12, which either do not publish an inrush function or duplicate a meter already included. No laboratory testing was performed and no measurements of our own are published.
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