Microtronics BLE mA Link, User Manual, Page: 18 / 46

5.1 Calculating the specified current value
The scale of the output signal is automatically adjusted to the measurement range of the gas sensor being
used. If, for example, sensor type H2S H7 (0-200 ppm) is used, a gas value of 0 ppm equates to an output
signal of 4 mA. At a gas value of 200 ppm, the output signal equals 20 mA. If the upper measurement range
limit is exceeded, a current value of 20.1 mA is issued until the maximum overload (1000 ppm on the H2S H7)
is achieved in order to signal error value "OF" (overflow). If the limit value for the maximum overflow is also
exceeded, a current value of 21 mA is issued to display error value "SC" (short circuit).
Lower measurement range limit (e.g. 0 ppm on the H2S H7) A
Upper measurement range limit (e.g. 200 ppm on the H2S H7) B
End of the output range for valid values (20 mA) C
Start of the output range for valid values (4 mA) D
Current gas measurement value E
Output current based on gas value F
Slope dependent on measurement range of the sensor (e.g. 0.08 on the
H2S H7) k
Offset dependent on the measurement range of the sensor (e.g. 0 on the
H2S H7) d
F = k * E + d
Note: Additional explanation of the behaviour if the valid measurement range is not observed
18 Rev. 01