Heating does not switch on, power supply seems to be sufficient

Precondition: cold outside temperatures, mainly below 0°C and in some but not all cases installation with very long cable length (>=100m)

• Device Shows "Error 18" in SOPAS
• Heating does not Switch on
• Commissioning test of heating fails

Cable length

While switching on the heating power (done by the LMS automatically by itself or when doing the commissioning test), the long cable length causes a relatively high inductance of the cables. This results in a "gap" of the power which is supplied at the sensor's end of the long cable. Then LMS5 detects too less voltage for the heating and will set an error message (18). The heating will remain switched off.

The whole procedure may restart after 1s as long as the temperature control of the LMS detects low temperature.

The LMS will continue measuring with specified accuracy as long as the components are able to operate even without heating.

It is not easy to verify this phenomenon by measurement, because the "gap" is very short.

This issue is not a problem of the LMS, but a result of the customer's installation.

This issue only occurs with very long cable length.

Cable diameter is too small for the used length of the cable.

Cable length

Insert a capacitor at the sensor's end of the cable, e.g. in the connection box.

Recommended type: 100uF to 470uF and 63V

Connect the capacitor between VS heat and GND heat, as close to the sensor as possible.
 

Check the used cable diameter and the recommendations from the operating manual.

If necessary, change the cable to a recommended one.

"Error 18" shown is in fact not a device error influencing the measurement Quality of LMS5. It is an Information or warning. The sensor is able to deliver correct measurement data as long as the device Status is OK. But anyway, it's recommended to ensure correct cabling for sensor power and heating power.

minimum Userlevel: Service