Norma DM950

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Norma DM950
Norma dm950.png
Status supported
Source code norma-dmm
Counts 21000
IEC 61010-1 CAT II 600 V, CAT III 300 V
Connectivity RS232, proprietary cable
Measurements voltage, current, resistance, capacitance, temperature, diode, continuity
Features autorange, data hold, bargraph, backlight
Website set.nl

The Norma DM950 is a 21000 counts, handheld digital multimeter with RS232 connectivity.

Models

The LEM Norma DM9x0 series of multimeters are 21000 count CAT II/CAT III hand multimeters with optional RS232 connectivity. The models differ by precision and feature set.

They were also sold as OEM devices by Siemens. The manufacturer was a company named Norma, later LEM Norma in Austria.

It seems that the same device series was sold with two different names and designs:

  • Norma Normameter 910..950 (red company sign and bumper; earlier)
  • LEM Norma DM910..950 (turquoise company sign and bumper, see pics; newer)
Norma LEM Norma Siemens OEM Precision (DC) Backlight RMS TRMS R 20 MΩ R 200 MΩ U AC 1 kΩ/V I 10A f C
Normameter 910 Norma DM910 B1024 [1] ±(0.5% +2d)
Normameter 920 Norma DM920 B1025 ±(0.5% +2d)
Normameter 930 Norma DM930 B1026 ±(0.3% +3d/+2d)
Normameter 940 Norma DM940 B1027 ±(0.1% +3d/+2d)
Normameter 950 Norma DM950 B1028 [2] ±(0.06% +3d/+2d)

The RS232 interface is optional. All models were available with or without RS232 interface. The RS232 interface was also available separately as an accessory.

These Norma multimeters use the term RMS for correct measurement of possibly non-sinusoid AC and TRMS for correct measurement of mixed-mode (AC+DC) voltages and currents.

The driver has been tested with a LEM Norma DM950 and a Siemens B1026 DMM. If you have a different multimeter of this series, we would welcome information if it works and what the ID string looks like. You can contact Matthias about it.

Hardware

Multimeter

  • Fuses
    • 2A: F 2A/250V DIN 41660-F2
    • 10A: FF 12,5A/500 V, >20kA/AC
  • TODO

Interface

The RS232 interface consists of the following components:

  1. Interface board (installed inside of multimeter, based on a NEC 75P116 microcontroller)
  2. Printer cable 5-pin to DB9
  3. PC adaptor (null-modem plug with slightly unusal pinout)

The RS232 interface is designed to allow a direct connection to a serial printer or data recorder. Therefore an adaptor is required to connect it to a PC.

Comm parameters (PC): DTR on, RTS off, RTS/CTS flow control (!).

If the interface cannot be powered from RS232 (e.g. RS232-USB converter with too low voltage), switching on the multimeter with the FUNC button pressed powers the interface from multimeter.

The interface board contains a battery-buffered clock and NVRAM memory.

The printer cable has got a power connector (10-16 V DC, 50 mA; coaxial power connector 5,5/2,1 mm) to power the multimeter and the interface externally. Opening the plug on multimeter side should be avoided, if possible, because the nut on the opposite to the screw is loose beneath the rubber bumper and it can be a bit tricky to get it closed again without removing the glued bumper.

Photos

Multimeter:

RS232 cable:

Protocol

Printer Mode

TODO.

PC communication mode

The multimeter supports about 50 commands. Most functions that do not require changing the position of the rotary switch can be remote controlled.

Command Reply Example Remarks
IDN?\n Device id and rev., interface rev. 1834 065 V1.06,IF V1.02\r ID string of a LEM Norma DM950, multimeter firmware version 1.06, interface firmware version 1.02
" " 1834 063 V1.04,IF V1.02\r ID string of a Siemens B1026, multimeter firmware version 1.04, interface firmware version 1.02
DATA?\n 27 chars ASCII + \r R␣␣␣␣␣␣␣␣␣␣␣␣␣149.10E+3␣OHM\r Similar to common 14 char protocol, but more verbose. ␣ means space.
STATUS?\n 20 hex chars + \r 03030024913100400040\r Binary data, value + status flags.
... .. .... More to do.

Measurement functions and ranges

Measurement function Range Resolution Accuracy sigrok result Remarks
V= 200 mV 10 μV ±(0.06% + 3) mq V, unit V, mqflags DC
2 V 100 μV ±(0.06% + 2) "
20 V 100 μV "
200 V 1 mV "
1000 V 10 mV "
V≈ 200 mV 10 µV ±(0.4% + 25) mq V, unit V, mqflags AC,DC,RMS
2 V 100 μV ±(0.4% + 10) "
20 V 1 mV "
200 V 10 mV "
750 (1000) V 100 mV "
V≃ 200 mV 10 μV ±(0.6% + 50) mq V, unit V, mqflags AC,DC,RMS There is no difference between RMS (AC) and TRMS (AC+DC) measurements except the accuracy.
2 V 100 μV ±(0,6% + 25) "
20 V 1 mV "
200 V 10 mV "
1000 V 100 mV "
V db≈ 62 - -42 dB 0.01 dB 0.5 dB mq V, unit V, mqflags AC,DC,RMS Actually 5 ranges.
V db≈ rel -42 - 52 dB 0.01 dB mq V, unit V, mqflags AC,DC,RMS
A=  2.0000 mA 100 nA mq Curr., unit A, mqflags DC
20.000 mA 1 µA "
200.00 mA 10 µA "
2.0000 A 100 µA "
10.000 A 10 mA "
A≃  2.0000 mA 100 nA mq Curr., unit A, mqflags AC,DC,RMS
20.000 mA 1 µA "
200.00 mA 10 µA "
2.0000 A 100 µA "
20.000 A 10 mA "
Ω 200.00 Ω 10 mΩ mq Res., unit Ω, mqflags -
2.0000 kΩ 100 mΩ "
20.000 kΩ 1 Ω "
200.00 kΩ 10 Ω "
2.0000 MΩ 100 Ω "
20.000 MΩ 1 kΩ "
200.00 MΩ 100 kΩ "
Diode mq V, unit V, mqflags DC,DIODE
Cont. mq Cont., unit ?, mqflags ?
Cap. F 2.000 nF 1 pF ±(1% + 3) mq Cap., unit F, mqflags -
20.00 nF 10 pF "
200.0 nF 100 pF "
2.000 µF 1 nF "
20.00 µF 10 nF ±(2% + 3) "
200.0 µF 100 nF "
2.000 mF 1 µF ±(4% + 3) "
Hz≃ 256 Hz 0.01 Hz ±(0.02% + 2) mq Freq., unit Hz, mqflags AC,DC
2.048 kHz 0.1 Hz "
16 kHz 1 Hz "
200.000 kHz 10 Hz "
°C Mo100/1000 –50 - +200.0 °C 0.1 °C 0.2% + 0.3 °C mq Temp., unit °C, mqflags -
Pt100/1000 -50 - +200 °C 0.1 °C ±(0.2% + 0.5 °C) " (min. temp. -273.1 °C?)
Pt100/1000 +200 – +600.0 °C 1 °C ±(0.2% + 1 °C) "
Hold mqflags += HOLD
Max mqflags += MAX
Min mqflags += MIN


Further functions?

The column "sigrok result" contains in short form what the driver generates for the resp. data type.

Resources