MT87 clamp meter

MT87 Digital Clamp Meter is the cheapest digital clamp multimeter I have found. It has been sold at price for less than 10 Euros/Dollars, while some other places sell the same mater often at around 20-30 Euros price.

Main Features:
● Mini and compact design, easy to hold
● Data hold and LCD display, easy and clear to read
● Low battery indication
● Overload protection
● Powered by 2 x AAA batteries ( not included )

Max. Display: 1999
DC Voltage range: 600V (1V resolution)
AC Voltage range: 450V (1V resolution)
AC Current: 20 – 400A (10 mA, 100 mA and 1A resolution)
Resistance : 200K Ohm

The meter has LCD with a max reading of 1999 Counts (Digital Multimeter). It has data hold button and low battery indication. The meter can measure DC and AC voltages using the test wires. The meter supports AC current measurements using the clamp (no support or DC current). The meter has buzzer, resistance measurement and diode test function. Standard accessories are multimeter, test leads and manual. The MT87 meter seems to be made by Zhangzhou Pinzhi Electronics Co., Ltd. This same MT87 multimeter can be found on sale at several brands and several different colors (yellow, blue and red) like in this picture from manufacturer product page:

It is a cheap digital clamp multimeter. It has Current Range from 0~400A AC, 450V DC voltmeter, Continuity/Diode Test Buzzer and Ohmeter 200K. The MT87 meter needs 2x AAA Battery Cell, it has a box, instruction manual and two wires for testing circuits.

The MT87 Clamp Meter is a portable instrument that measures the AC current of a circuit without breaking the circuit. he instrument is mainly composed of an electromagnetic current meter and a sleeve type current transformer. When the wrench is pressed, the core of the current transformer can be opened, and the wire through the current can be cut through the opening of the core without being cut. The circuit conductor to be tested passing through the core becomes the primary coil of the current transformer, and a current is induced in the two coils by the current. Therefore, an ammeter connected to the two coils can be used to indicate the current of the measuring line. This measurement methods allows measuring quite large currents without need to cut the circuit being measured or even touch the bare electrical wire (you just need to get the clamp sound the single wire carrying the current).

MT87 has AC current measurement range from 0~400A AC, so it’s pretty much for heavy duty measurements. The current measurements are done with the current clamp put over the single wire being measured. This meter support only AC measurement for current, and this meter cannot measure direct current in any way. There are three ranges for alternative current (20A, 200A and 400A), with resolution down to 10 mA at 20A range. The clamp meter works OK for AC current measurements et 50 Hz (I tested from 100 mA to almost 100A). With clamp meters typically the current measurements are accurate to within 5% or so, and the position the wire inside camp can have some effect on accuracy. With MC87 the current measuring accuracy is decent for a cheap clamp meter, within few percent compared to other clamp meter. The clamp meter has an useful Data Hold function, which when pressed, displays the current data from LCD screen until you press it again to reset. Hold feature is nice to have. The clamp mechanical construction feels a bit cheap but still OK.

For resistance measurements the meter has combined Continuity test / Diode Test mode with piezo buzzer for the continuity test. The diode test uses 1.2 mA current and maximum 3.2V open circuit voltage. In diode measurement the meter shows the approximate diode forward voltage or “1″ when no current flows. The continuity buzzer beeps when there is less than 75 ohm resistance between measurement leads. This works OK for basic continuity testing needs. The resistance measurement functionality that can measure resistance values up to 200 kohms. The resistance measurement is auto-ranging with two measurement ranges built-in: 2 kohms (1 ohm resolution) and 200 kohms (100 ohms resolution). The manufacturer promises protection up to 300VAC/VDC peak for those ranges (I did not test if meter could really withstand that).

There is 600V range for direct voltage measurement and 450V for alternative current measurement. Those measurements are done with the test leads. The voltage measurement works OK at low voltages. I did not try those ranges at high voltages, because that did not feel safe to use because thee test leads feel quite poor and I would not be willing to try measuring 600V with them even though they say 1000V voltage rating marking on them. The worst thing is that the banana connectors that plug to the multimeter terminals are not properly shrouded banana plugs and are quite loose. They do not feel like that they would stay properly in place when making field measurements, and when they come loose the metal part is clearly visible. So trying to measure mains voltage with those is a potential hazard.

I think those leads would not meet the EU safety regulations for multimeter test leads. The sockets on the multimeter cannot take better quality well insulated test leads, so it is hard to replace them with better.

I found two review articles on the meter on Internet: MT87 Digital Clamp Multimeter Hands On and MT87 Digital Clamp Meter Review. I can agree with most details on them.

The review article MT87 Digital Clamp Meter Review makes a claim:

The problem with this device is the polarity of the voltmeter, if I measure a battery in reverse. It does not display a minus sign to indicate a reverse polarity.

I verified with my meter and could not replicate this issue. My MT87 on the DC range show the DC voltage polarity correctly, showing the minus sign on the display when negative voltage is measured.

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When I bought the meter originally, I planned to do a teardown of it to see what is inside. I did not have time to do it immediately, so some other people made it before me. There are teardown pictures at MT87 Digital Clamp Meter Review article and two videos with teardowns, so I don’t see a point in doing another myself. Inside the meter the main components are a lot of SMD components, two LM358 op-amp and the black blob IC that does the measurement. The internal construction generally seems to be quite decent for a cheap meter in overall construction, but there does not seem to be much protection components or large insulation distances between traces for the high voltage inputs like in “better” multimeters.

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