E3. Analog output wiring

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.

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.

Example:

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:

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:

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:

• E4. Ethernet wiring
• E5.Wring for air audits