BCM-MS, BCM-LS
3.3.1 Analog Current Outputs (4..20 mA) - Measurement Without Load Resistor
The current should be measured with a suitable ammeter as shown below.
Sensor cover top view
Fig. 6: Measuring the analog 4...20 mA outputs without load resistances
[> page 17] for how to allocate the measured current to the parameter.
3.3.2 Analog Current Outputs (4..20 mA) - Measurement With Load Resistor
To measure the currents of the analog current outputs, a load resistor must be connected to each output as shown below. De-
pending on the supply voltage, the load resistance should be between 25 Ohm and 200 Ohm. A voltmeter can now be used to
measure the voltage which drops over the respective resistance.
Sensor cover top view
Fig. 7: Connecting the load resistances to measure the analog 4..20 mA outputs
The default configuration is intended for oil temperature on channel 1 and relative humidity on channel 2.
The channel assignment can be changed and is described in chapter
Setting Analog Current Outputs
3.3.3 Load Resistor Size
The load resistance cannot be selected arbitrarily. It must be adjusted to the supply voltage of the sensor. The maximum load
resistance can be calculated using the formula (6 -1). Or you can alternatively use the table here.
R
max
/ Ω=U
Supply
/ V ∙ 25 (Ω/V) – 200 Ω
25 Ω ≤ R
max
Ω 200 Ω
(6-1)
R
max
in
Ω
U
supply
in V
25
9
50
10
100
12
150
14
200
16
Tab. 10:
Determining the load resistance based on the supply voltage
16
Bühler Technologies GmbH
BE150104 ◦ 03/2021
