The analog signals (temperature sensors) are connected to the analog-to-modbus device ADAM 4117 or EX9017. The ambient temperature sensor is usually a Comeco TSOP.
1. Visit the Inaccess SCADA panel. Check if the ADAM4117 or EX9017 is powered on. You can confirm that by the led on the devices.
2. Each sensor is power supplied with 24 Volts and the return cable is connected to the terminal blocks (and consequently to ADAM or EX) as shown below. The power supply is connected on the terminal blocks 1,3,5 etc (that are bridged)
3. Visit the ambient temperature sensor. On terminal + the 24VDC power supply is connected. On terminal - the return cable is connected. Measure the dc voltage between terminal + and a grounded part (not between + and -). This voltage should be 24V.
4. Disconnect the cable from terminal - and measure the dc voltage between terminal - and a grounded part.
It should be 22-23 Volts. If it is 24 or 0 Volts, the sensor is malfunctioning and needs replacement.
5. Connect again the cable to terminal -.
6. Return to Inaccess SCADA panel.
According to the Detailed Design file find in which AI chanel of ADAM4117/EX9017 the module temperature is connected. Let us give an example.
Let’s suppose that the Detailed Design file claims that ambient temp. sensor is connected to AI0.
The general correspondence in all sites is
AI:0-> terminal block 2
AI:1-> terminal block 4
AI:2-> terminal block 6
Disconnect the cable from terminal block 2 (it is the return cable). Measure the voltage between this cable and the ground terminal. It should give approximately the same value as in step 4. If it is 0 then the cable between the sensor and Inaccess side is broken and the technician needs to replace it.
If the value is the same as in step 4 then probably the problems stands on the channel of ADAM/EX.
7. If the checks in all above steps are successful, you can change the return cable to a spare chanel (for this example spare terminals are 8,10) and call Support in order to read the value to the new chanel.