Specification - arup-group/pqm-hellebores GitHub Wiki

Electrical supply

Voltage                                 : 230 V AC
Frequency                               : 50 Hz
Supply fuse                             : 3.15A type T ceramic cartridge

ADC

Channels                                : 4
Resolution                              : 16 bits
Sample rate                             : 7812.5 Sa/second synchronous all channels

Display

Resolution                              : 800 x 480 pixels IPS
Control                                 : capacitive touch
Update rate                             : up to 70 waveform updates/second
Measurements                            : 1 update/second

Services

Operating system                        : Raspberry Pi OS (32 bit Debian 12 'bookworm')
Network                                 : Wifi
Software update                         : OTA Github
Time service                            : NTP server pool
Remote access                           : SSH, VNC
Measurement log file                    : 1 update/second, CSV format
File transfer                           : Wifi+SCP or Bluetooth
Keyboard                                : Virtual on-screen or Bluetooth

Voltage

Peak                                    : 450 V
Uncertainty                             : ± 1 % of reading
resolution                              : 0.1 V

Current

Continuous                              : 3 A RMS
Peak (full range)                       : 20 A
Peak (low range)                        : 0.4 A
Uncertainty (full range)                : ± 1 % of reading + 0.002 A
Uncertainty (low range)                 : ± 1 % of reading
Resolution                              : 0.001 A
Shunt resistance thermal coefficient    : 50 ppm /degree C

Power

Continuous (230V systems)               : 650 W
Uncertainty (full range)                : -4 % / +1 % of reading + 0.03 W
Uncertainty (low range)                 : -4 % / +1 % of reading + 0.003 W
Resolution                              : 0.01 W

Reactive and apparent power

Continuous (230V systems)               : 650 VA
Uncertainty (full range)                : -4 % / +1 % of reading + 0.30 VAR/VA
Uncertainty (low range)                 : -4 % / +1 % of reading + 0.03 VAR/VA
Resolution                              : 0.01 VAR/VA

Earth leakage

Peak                                    : 10 mA
Uncertainty                             : ± 2 % of reading + 0.010 mA
Resolution                              : 0.001 mA

Frequency

Uncertainty                             : ± 0.005 Hz
Resolution                              : 0.01 Hz

Power quality

Power factor                            : ± 3 % of reading
Crest factor                            : ± 3 % of reading
THD(v)                                  : ± 5 % of reading
THD(i)                                  : ± 5 % of reading
Harmonic coefficients                   : ± 3 % (h0 to h11), 5 % (h12 to h23), 20% (h24+) of reading

Energy

Uncertainty                             : -4 % / +1 % of reading
Resolution                              : 0.001 Wh

Reactive and apparent energy

Uncertainty                             : -4 % / +1 % of reading
Resolution                              : 0.001 VARh/VAh

Notes:

  1. Power quality (current) uncertainties are valid where device-under-test has peak instantaneous current in the range 0.2-10.0 A (full range) or 0.02-0.4 A (low range).
  2. There is a small offset current and apparent power due to noise in the current measurement channel. When taking measurements of low power devices, this error can be minimised by using the 'low range' setting.
  3. The shunt resistors, by-pass diodes and NTC thermistor are wired in series with the load and introduce some ‘voltage drop’ at the device-under-test. This is allowed for in a wider uncertainty band for power and energy measurement.
  4. There is an offset earth leakage current due to stray effects in the measurement circuit and capacitance in the measurement cable. The correction can be found by unplugging the device-under-test.
  5. The NTC thermistor controls peak inrush current to protect the meter. A transient capture can provide insight into the inrush event, but note that in the field the peak current will be higher and the duration shorter. In addition, transient and high frequency components of earth leakage current are electrically suppressed with a ferrite core.
  6. The single-pole load switch on the meter is suppressed with an RC snubber. The snubber passes a small amount of current: to fully isolate the device-under-test, you must unplug it.
  7. The meter can operate on a 120V 60Hz AC system with a component change: refer to project report.