Installation and Operation Guide | DGS Modbus
RS8HJ102 | 11
© Danfoss | ADAP-KOOL® | 2016.12
4.3 Adjusting the Alarm Setpoint
Function
Description
1
Locate P1 and use it to adjust the set point at which the relay
activates.
2
Using a volt meter, monitor the output between test points
0V (negative) and ALARM (positive) until the correct setting is
reached. See formula below for example of how to calculate the
desired setpoint.
Voltage = Alarm Value × 5 V____
Max Range
Voltage: The potentiometer is adjusted until this signal is mea-
sured between the test points
Alarm value: The ppm level at which the sensor must signal an
alarm on the relay and on Modbus
Max range: The maximum measurement range of the particular
DGS sensor
Example: For a sensor range of 0-1000 ppm, calculate the voltage
to set the alarm point at 100 ppm.
Voltage= 100 ppm × ___5 V____
1000 ppm
= 0.5 V
So the alarm voltage setting is 0.5 Volts.
NOTE
: The output changes when changing P1. It does not change
when changing the Modbus value.
The alarm setpoint may be changed physically via the potentiom-
eter P1 (see below) or through the Modbus interface (see section
7).
If the Modbus setting takes a value different than ‘0’ (zero), the
Modbus setting takes priority.
As default the potentiometer setting takes priority (that is, the
default Modbus setting is ‘0’ (zero)
For all DGS gas detectors the process to adjust the alarm setpoint
via the potentiometer and test points ‘TP3 0V’ and ‘TP1 (Alarm) is
the same.
See Figure 1 for locations.
Alternatively this may be set via Modbus directly in ppm or % of
full scale.
See section 7 for details.
NOTE
: A Modbus setting takes priority over the hardware setting.
If needed set the Modbus value to zero to re-activate the hard-
ware setting.
For R449A the maximum allowed alarm setpoint is 500 ppm.
