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RS PRO S2 - 01 - Front.png
Status in progress
Source code appa-dmm
Counts 6000
IEC 61010-1 CAT III (1000V) / CAT IV (600V)
Connectivity Bluetooth LE
Measurements voltage, frequency, resistance, continuity, diode, capacitance, current, temperature
Features autorange, data hold, min/max, relative, non-contact voltage detection hi/lo, backlight, true-rms, data logging, single value storage, auto-v/loz, VFD, built-in magnetic sticker, µA current range

The RS PRO S2 is a 6000 counts, CAT IV (600V) / CAT III (1000V) handheld logging digital multimeter with Bluetooth LE connectivity and long battery duration. It is marketed as a "HVAC Multimeter" (optimized for the needs of heating, ventilation, and air conditioning technicians).

It is based on the APPA S2, See also: APPA Multimeters.

A sigrok-driver supporting these APPA-based devices ("appa-dmm" in sigrok) has been created and will be included in mainline sigrok once it passes acception (see developement repository branch appa-dmm).


  • MCU: Atmel ATSAML22N18A-U
  • ADC-ID: Hycontek HY12P65
  • BLE-SoC: AMICCOM A8105
  • Fuses:
    • Current range 400mA: Amp rating: 0.44A, Voltage rating: 1kV, Interrupting rating: 10kA, Opening: Fast acting, Size: 10mm x 34.9mm
  • Power supply: 2 x IEC LR6 1.5V (works fine with IEC HR6 1.2V)

Photos and Teardown


Unless noted otherweise, the tests in this section have been performed by Cymaphore on a RS PRO S2, Firmware v2015 / 808

Usage of rechargable NiMH batteries

The device works acceptable with rechargable batteries. Voltage boundaries are however a bit unsuitablefor NiMH cells, battery cut-off level of 1.14V/cell is to early, even for alkaline cells, this way the full capacity of the cells can not be used.

Battery indication

  • FULL: >2.86 V (~ 1.43 V/cell)
  • HALF: >2.68 V (~ 1.34 V/cell)
  • LOW: >2.46 V (~ >1.23 V/cell)
  • WARN: >2.28 V (~1.14 V/cell)
  • Forced POWER-OFF: <2.28 V (~ 1.14 V/cell)

Current consumption

Test supply voltage: 2.4 V


All functions measured, average value over measurements taken.

  • Device active: 2.952 mA
  • With Bluetooth LE active in standby: 4.211 mA
  • With Bluetooth LE in active data acquisition: 7.538 mA
  • With display backlight on: 17.251 mA

If the device is in APO or low battery power off mode, it consumes 9µA.

Based on that numbers, with backlight off the device should be able to surpass the battery duration specified in the datasheet by a lot, making long duration logging sessions possible.