DMR35-DCxA.A01.D04 Page 4 of 8

DMR35-DCxA Series

DMR35 DC Micro and Milli-ammeters

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POWER SUPPLY CONNECTIONS

The meter is powered through the +VS and –VS terminals and requires a DC power supply which may range from 9VDC to 32VDC. This supply is

electrically isolated from the meter’s measurement electronics, so that the meter’s measurement input terminals (+I_IN, -I_IN) do not need to be

connected to the meter’s power return terminal (-VS), and may vary as much as +/-48V from this connection. Please note that the meter’s isolation

barrier is intended only to simplify measurements, and not for safety purposes – the maximum voltage between the power supply terminals (+VS or –

VS) and the measurement input terminals (+I_IN, -I_IN) must be limited to +/-48VDC. The DMR35 series of meters incorporates protection against

momentary applications of both overvoltage and reverse polarity to the power supply(+VS, -VS) terminals. Depending on regulatory and application

requirements it may also be necessary for the user to add external fusing.

MEASUREMENT INPUTS

Current to be measured by the DMR35 is passed through the +I_IN and –I_IN terminals. This requires that the meter be inserted in the line in which

the current is to be measured. Unlike many panel meters, the DMR35 series’ measurement inputs are electrically isolated from the power supply

terminals, which allows for fully differential measurements over a common-mode range of +/-48V with respect to the power supply terminals +VS or -

VS.

CONNECTION EXAMPLES

The schematic below shows how a DMR35 DC current meter can be used to perform a ‘high-side’ current measurement, where the meter is inserted

into the load’s positive leg. In this example, the meter is powered from the same power source powering the load, and the meter’s current sensing

terminals (+I_IN, -I_IN) are at a potential of 12 volts higher than the meter’s negative power terminal (-VS). The meter can also just as easily be used

to measure current in the load’s negative leg (‘low-side’ current sensing).

It is also possible to use the meter to monitor voltage in a circuit that is independent of the meter’s power supply circuit, as shown in the schematic

below. When used in this way, the meter’s current measuring terminals may electrically float with respect to its power supply terminals, as long as the

voltage difference between the two terminal pairs remains within +/- 48V of each other.