4-20mA Transmitter Boards

Alphasense, established supplier of electrochemical gas sensors, also offers 4-20 transmitter circuits for use with both toxic gas and oxygen sensors.

Alphasense offers both analogue and digital transmitter boards for use in fixed installation systems.

Analogue and digital boards are interchangeable: both have the same dimensions, pillar locations, 2-wire connectors and 4-20mA output.

	Analogue Transmitter	Digital Transmitter
Oxygen sensor		-
B Series sensor
A Series sensor	-
NO, ETO Biased sensor	-
Potentiometer calibration		-
PC Software calibration	-
Temperature compensation	-
PC software rescaling	-
7.5 to 35 VDC supply		-
10 to 30 VDC supply	-
4-20mA output
USB output (with adaptor)	-
BS EN61326 certified	-

The boards supplied with sensors are pre-calibrated. The 4-20mA output signal provides an equivalent performance to that shown in individual sensor data sheets provided for each of the Alphasense sensors, but scaled to specific range requirements.

The 4-20mA current is linear from 0ppm (4mA) to your specified full scale concentration (20mA). The voltage measured across a resistor in series with the supply current (typically 100 ohms) will give an accurate measurement of gas concentration.

Each board is provided with a set of mounting pillars for location of the board into an enclosure.

To allow OEMs to distinguish their product from other offerings, the sensor-to-gas aperture design is left for the OEM to execute.

Table 1 shows maximum gas concentrations