Digital Panel Meters



96 x 48mm digital panel meters with 3.5 digit, 14.2mm high 7 segment LED’s. The products offer a wide range of AC or DC input parameters. Essentially there are 3 main product group types:- AC Volts, Amps, Milliamps, DC Volts, Amps, Milliamps, Millivolts, Frequency.


With the combination of mA input M300-AD1 and the M100 series Power transducers, parameters such as kW, kV, Ar etc can be measured and displayed. Customer adjustment of botjh “ZERO” and “SPAN” is permissible via potentiometers, accessible from the rear of the product.


Meter rear view

The 96 x 48mm case is designed for fast and simple installation, using the corner brackets for panel mounting. The M3.5 terminals allow the use of traditional termination and no extra terminal kits or soldering to PCB’S are required.

Theory of operation

AC Inputs

Both AC Voltage and Current circuits are average sensing RMS calibrated. The input signal is transformed to a low level of AC. The transformer secondary voltage is fed to a precision active rectfier. The resulting DC signal is presented to an analogue to digital A/D The A/D converter uses the dual converter slope integration method of conversion. The resulting digital information is used to drive the LED display.


DC Inputs

DC Voltage and current inputs are fed into high stability ranging components. The ranging components reduce the input signal to a 2 volt level. If the input is below 2 Volts and amplifier is employed to derive 2 Volts. The 2 Volt signal is then presented to the A/D converter which provides the digital information to drive the LED display.

Frequency Inputs

A Frequency to Voltage F/V converter is used to convert the output signal to a DC signal. The resulting DC signal is fed into the A/D converter and the same process as in the AC and DC circuits previously described takes place.

General Specifications

AC VoltsM300-VAD0..600V
DC VoltsM300-VD1± 50/60/75/100/150mV
DC VoltsM300-VD2± 50mV…1999mV
DC VoltsM300-VD3± 2V …199.9V
DC VoltsM300-VD4± 200V …600V
AC AmpsM300-AAD1 or 5 AC (0.2 to 10A)
DC AmpsM300-AD1± 1/5/10/20
DC AmpsM300-AD2± 100µA…199.9µa
DC AmpsM300-AD44/20mA


M300-VAD10K Ohm/V
M300-VD1/2> 100K Ohm
M300-VD3/410K Ohm/V
M300-AAD< 2VA
M300-AD1/2/3/420mV drop
Current4 x continuous
25 x 1 second
Voltage1.5 x continuous
4 x 1 second
Accuracy± 0.05% of reading ± 1 digits
Linearity± 1 digit roll over error ± 2 digits
ConversionDual slope integration
CMRAC 50dB 50 to 60Hz
DC 25 1K Ohm source unbalanced


Working Temperature0-60 deg C
Function Temperature-25 to +70 deg C
Storage Temperature-55 to 85 deg C
Temperature Coefficient0.01% per deg C
Relative Humidity0-95% non-condensing
Warm up time1 min
Shock30g in 3 planes
Test Voltage4kV RMS 50Hz 1 min


AC Voltage115/230/400 Volts (±25%)
45 to 65 Hz Burden < 2VA
DC Voltage24/48/110 Volts (± 20%)
Galvanic isolation. Burden < 3W


Digits1999 Full scale
Size14.2mm (0.56″) 7 segment red
Decimal PointInternally selectable
Overrange indicationDisplays “1” or “-1”
Update response time< 1 second
PolarityAutomatic with (-) indicating negative inputs


DIN caseDimensions 96 x 48 x 98
MaterialBlack Polycarbonate Complying with UL94VO
TerminalsScrew type for 2 x 0.5-3.5mm
Enclosure codeIP 54 NEM A 12 Optional IP65 NEM A4

a) All inputs (AC or DC) are connected via terminals 1 & 3
b) All Auxiliary supplies (AC or DC) are connected via terminals 6 & 8
c) Access to the “ZERO” & “SPAN” adjustment. Remove terminal
blanks in position 9 & 10. ZERO = 10,SPAN = 9
d) Optional externally selectable decimal point. 16=common, 15=1.999
14 = 19.99, 13=199.9 Link 16 as required.

DP-dig dim

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