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E3. Analog output wiring

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1. Introduction

The analog output can be used for:

4..20 mA as the output of flow, pressure or temperature
Pulse output
Alarm output

All outputs can be wired into a central data acquisition/building management system or the analog input of a PLC. See chapter E1 for wiring requirements.

Specification: The output is an active current loop, non-isolated and linearized.
This means: The positive wire is shared between the power supply of the VPFlowScope and the analog output.

For the analog output only pin 1 till 3 are needed, and the loop can be closed by connecting the 4..20 mA. output (3) back to pin 2 (0 Volt) through, for example, a multimeter or an analog input module.Icon M12 5-pin

1+12..24 VDC.
20 Volt.
34..20 mA output.


2. Using the 4..20 mA output

2.1 Electrical scheme

The current meter is placed between the current output and the power supply ground wire.

Electrical scheme analog output


The live-zero represented by the 4 mA. allows the receiving instrument to detect a failure of the loop.

An analog current loop can be converted to a voltage input with an external precision resistor, for example a 220 Ohm resistor. Place it between the 4..20 mA output and the 0 Volt pin. 4 mA will result in 0.88 Volt, and 20 mA will result in 4.4 Volt. This is a good match for a 0..5 Volt input.

3. Pulse

The output will be:

  • 0 mA: means the idle state.
  • 20 mA for 1 sec., followed by 0 mA the next second (idle again): means a pulse state.

The pulse connection is non a potential free contact, so add an isolator if a potential-free contact is needed.

Electrical scheme:

Electrical scheme pulse

Example: see chapter 2 above only replace the analog meter by a pulse counter or an isolator.

4. Alarm

The output will be:

  • 0 mA: means Idle state
  • 20 mA: means alarm.

Electrical scheme:

Electrical scheme alarm

For switching on lamps or buzzers: An external control current relay is required. When selecting a relay, make sure that the input can be controlled by a current signal. (Chapter G11)

5. Next Step

another way to set up your VPFlowScope:


Updated on December 31, 2020

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