Author Topic: RS PRO S2 (APPA S2) review and pictures  (Read 332 times)

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Offline Cymaphore

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RS PRO S2 (APPA S2) review and pictures
« on: June 04, 2021, 03:50:16 pm »

since I mentioned the meter already in other threads, I want to give a firm introduction to my (private) other good meter, the RS PRO S2. I got it originally to finalize my sigrok-driver for the APPA DMMs, it has the same protocol and Bluetooth functionality as the BENNING MM 12 (APPA 506B) I already had.


The S2 is a field meter for electrical engineering optimized for HVA usage.

Generally the meter is part of the S-Series build by APPA, with each model specialising in one field usage area:

  • S0: Basic, no logging, no current, no HFR
  • S1: Industrial, A-range
  • S2: HVAC, µA-range, Temperature
  • S3: Photovoltaic, A-range, Temperature, 1500V/2000V measurement range, no LoZ/Auto-V
Otherwise the meters have the same fundamental Functions and a very nice (because simplistic) Bluetooth App as remote display and for log download.
The APPA S2 is also available as BENNING MM 10-1. See here for a listing of brands these devices are available under as far as I could research.


  • Displays at a rate of 3/s, quick reaction to changes
  • 6000 Counts
  • 0.5% basic DC Accuracy
  • Compact for a CAT IV device
  • Very fast autoranging in voltage modes, usually under 1/2 of a second (eyeball measurement) depending of the direction. Rolls over at 6500.
  • Excellent display backlight (blue-ish) and flawless viewing angle. Light "inversing" effect from the top when backlight on, that doesn't affect the readability at all.
  • Bargraph that updates faster than the display readings by my perception but slower than the BM789
  • Bluetooth LE (App for remote display and log download available, sigrok-support in my github-branch)
  • Datalogging
  • Built-in magnetic booth
  • Bargraph ranges: 0 ... 60 (ACV, ACA, Ohms, Cap, Diode) and -60 ... 0 ... +60 (DCV, DCA)
  • Auto power off can be disabled or configured to different values (5, 10, 20 minutes, off)
  • Backlight stays on unless commanded to do otherwise! :-)
  • Very fast continuity buzzer with red LED for visual indication
  • Temperature measurement, Type K
  • µA-Range
  • LoZ AutoV
  • Very nice rotary switch, easy to one-thumb it single-handed
  • Min/Max, Hold, Rel, Manual ranging, HFR
Other specs and ranges, etc., see here.

I put some other details, battery usage and Chipset details on it's sigrok page.
Measurement performance

One of the main selling point is it's speed by my perception: Ranging happens usually almost instantly, when using it in a setup together with Fluke 179, Fluke 117 or my MM 12 it's usually the first one to show the result and usually only takes another display update to give the final reading (except for very high resistance, where it takes a couple of readings to settle down).

Small Capacitors are virtually instantly measured, 1mF electrolytic take about 4s. Measurement of 600Ohm and 6k ranges take, including ranging, about 2s, 10k and up about half a second to a second.

Reaction to changes is quite rapid, it usually doesn't miss short changes in voltage signals (for example short voltage drop because of switching), but not as good as the BM789s bargraph by quick comparison. Bargraph is about as fast as that of the flukes I know that have it, but not nearly as fast as that of the BM789.

Bargraph with two ranges automaticalls switches between 0 ... 60 for AC and -60 ... 0 ... +60 for AC with "0" in the middle.


You can crawl under a car, stick it to the bottom plate and single handed operate it. Backlight stays on, readings are fast, and if you have to crawl out to switch something you can activate bluetooth and continue to read the measurements. At lunchbreak just activate the logging and once you come back have a look if "strange rare event" shows up in recorded data.

It doesn't care, so far, that it fell of a cabinet roof, through a motor compartement, and a couple of times of the bench. So far it didn't complain or malfunction because of that. Display light stays on, I usually have APO permanently off.

It runs on 2 AA-cells and works fine with NiMH cells. Battery life is quite good.

Originally I purchased it just to make a sigrok driver for these Models out of interest, but now I really like it as field meter. I occasionally have them both together in SmuView, to measure incoming/outgoing values or "power" or such things over ble with my notebook.

Voltage input seems adequitly protected, mA/µA range is designed for HVA usage (flame sensor) and underprotected by my practical experience (damaged it with switching events unintentionally, but repairable). It's the meter I primarily built the ruggend compact shunt for, so that I can carry it standalone somewhere and still have a decent A range at hand :-)

The display is great by my perception, good lighting, good readability, good speed.

Unfortunately it doesn't have a 60mV range, that I miss on it, also the frequency measurement is limited to 100kHz, but that doesn't matter to me personally.

It also only has 6000 Counts. That I find useful, because where and when I use it there is no need for a higher display count and more digits are rather in the way and irelevant.

NCV is present on the device and called "Volt Seek". Works well, but I personally dislike the function, independent of the vendor.

If you have any questions about it or want me to run something with it, just let me know.

Best regards,

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