Quick Review of the ennoLogic eM860T True RMS Multimeter

I picked up an autoranging True RMS multimeter from ennoLogic a couple of weeks ago. Before this purchase, I actually had never heard of ennoLogic. But the design and spec of the meter looked quite good and the selling price was not bad for a 6000 count meter at all. So I bought one to try out.

The meter was packaged in a generic box with a stick-on ennoLogic label. From a first glance, this looked like a re-badged product as most name brands pay much more detail to their products packaging.

case

The meter and accessories are inside a nice little pouch. It even came with a very detailed color-printed user manual. The included K-type thermocouple does not come with the standard thermocouple leads however, instead it uses the standard banana plugs.

pouch

The meter itself looked very sturdy. It is significantly larger and heavier than my BK precision 2709B, the picture below shows these two meters side by side:

eM860T_2

The contrast of the LCD is pretty good although BK precision 2709 probably has slightly better viewing angle. The white LED backlight of this meter looks gorges.

eM860T_1 eM860T_0

The range switch feels solid. It is a bit on the stiff side however, making it difficult to switch ranges with one hand if not pressing hard on the meter. I do like the separate V and mV ranges. This makes some routine measurements much more convenient. For comparison, on the BK 2709B measuring using the mV range requires pressing the range button 5 times. Further more, eM860T has two ranges (60mV and 600mV) in mV position. This means that you get one extra decimal when measuring voltages under 60 mV (e.g. two decimals instead of one).

With an update rate of 3 readings per second, eM860T feels faster in most of its ranges compared to the update rate of BK 2709B. The resistance range is a noticeable exception however. When in auto-ranging mode, range switching in resistance mode is painfully slow. It takes almost 3 seconds for the meter to cycle through all the ranges before settling on a final reading which is considerably slower than the almost instant range-switching of the BK 2709B in resistance mode.

I also like the capacitance measurement on the eM860T a lot. First, the capacitance mode shares the same input socket as the voltage and resistance measurement range which means switching between voltage and capacitance measurements does not require swapping the leads (you have to do this with the BK 2709B). Also, many meters have trouble measuring high capacitance capacitors. BK 2709B for example, while is rated for measurement up to 66 mF it routinely fails to measure capacitance higher than a few thousand micro farads. The ennoLogic eM860T on the other hand, while is only rated for measurement up to 6 mF it can measure capacitors with high capacitance (e.g. 10,000 µF) without any problem.

The following is a picture showing the inside of the meter with the back cover removed. Note that the 9V battery sits in a separate compartment which can be accessed by removing two threaded screws on the battery panel on the back. As you can see, the PCB is well made and most components are surface mounted.

eM860T_3

Here is a closeup of the main chip DTM0600L (the only documentation I could find was in Chinese), which handles all of the measurements of the meter. The 2K EEPROM (24C02A) stores all the calibration constants and configuration parameters. As far as I know, there are quite a few other multimeters (such as Tekpower TP40, UNI-T 139C and Velleman DVM4100) also use the same IC.

eM860T_4

The main processor and the EEPROM is powered by 3V via a linear regulator (shown below). I am curious as to why they decided to use a 9V battery rather than say 2 AA batteries as the operating voltage for DTM0660 can be as low as 2.4V. That said, you can run the 9V battery all the way down to below 4V before the regulator loss its regulation. So given the relatively low current consumption at just around 1.5 mA, even a 9V battery should last a long time.

eM860T_5

Towards the top of the PCB, there was a populated header for I2C. The inclusion of a calibration switch indicates that all calibration is done in software, not via hardware.

eM860T_6

Here is a picture showing the PCB removed from the case:

eM860T_7

Here is a close up of the two massive HRC fuses. These high rupturing capacity fuses are necessary because this meter is CAT IV rated. I have not seen many multimeters in this price range (around $65) with a CAT IV rating.

For most electronics work, a CAT II rated multimeter is more than adequate. If you have the occasional need to measure voltages in a distribution box, then you will need a CAT III rated meter. So a CAT IV meter is probably an overkill for most hobbyist but the added safety gives you extra confidence when working on mains connected circuits.

The input jacks are soldered directly onto the board, which does raise some long term reliability concern. That said, if designed correctly, these jacks should withstand the forces applied during normal use.

eM860T_8

Here is a picture with the meter further dissembled:

eM860T_9

You can clearly see the robust input protection circuitry here:

eM860T_10

And in the picture below, you can see the reverse side of the PCB. The marking on the etched contact switch is intriguing. The second switch is labeled “REL/PC Link”, so presumably this board is used for the RS232 version of the meter as well (although this is the only ennoLogic meter I have seen so far).

eM860T_11

One thing I didn’t quite like about this meter is its NCV (non-contact voltage detection) feature. When in NCV mode, any static discharge (even just by touching the top of the meter) would cause the meter to beep. And when a 120V live wire is placed near by, the detector is actually not sensitive enough to detect it. During my experiment, the only way that I could set off the NCV alarm consistently was to place the wire directly against the detection surface towards the top.

For the price of the meter though, it remains an excellent choice if you can stand the slow resistance measurement and the not-too-useful NCV function.

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7 Comments

  1. goetz says:

    Hey Kerry,
    you wrote:”The inclusion of a calibration switch indicates that all calibration is done in software, not via hardware.”
    in the datasheet translation i found:
    12. Calibration procedure
    Key assignment in Calibration mode:
    SELECT: skip/function select
    HOLD: subtract (-)
    Other keys: add (+)

    so isn’t that just a jumper to enter calibration mode?
    i cant check it. i’m waiting for my ut139 that has just holes in the pcb as i can see from pics

  2. Gipi says:

    Hi Kerry!

    I would like to ask for help!

    Given a PEAK HOLD HP 760H type instrument DTM0660L and 24C02A chip EEPROM.
    The instrument is a jumper, which can be normal or CAL (calibration) position.

    CAL mode, the instrument has been started. In this case, it runs like a “self-test”, why in the end
    “Erro” appears on the display.

    But when the jumper is back to normal mode, you can not measure or fully give incorrect results.
    (Rupture test: continuous beep, DC: 3.6V Li-Ion battery to 7.4V has a measuring capacity: each case is too high (OL), etc.).
    Question: back somehow possible to restore the original (initial) values, and if so, how?

    Thanks!

    Gipi
    Hungary
    (I do not speak English. Google translator made)

    • kwong says:

      According to the very limited information I could find in the original Chinese manual, the display of an “Err” (followed by a number 0~4) indicates something is wrong with the measurement circuitry. However the manual did not explain much but did suggest that it could be a fault in one of the voltage dividers. Unfortunately, that’s all the information I could find.

  3. Gipi says:

    Hi Kerry!

    I’m sorry! Very hopeful.
    For me, the display “Err0”.
    I thank you very much !!

    Gipi

  4. Ajay More says:

    Hi Kerry,

    You did a good job with the review. I’ll be grateful if you could provide me a details of input protection circuit used in this meter. A rough sketch will be sufficient for me. I am trying to learn different techniques of multimeter input protection. Your review suggests that 860T has a very good input protection. So out of curiosity I want learn the details of it.

    Thanking you in advance.

    Regards,
    Ajay

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