tan-tonge avatar image
tan-tonge asked

IMT Irradiance Sensor - Cerbo GX - Not Connecting Properly

I am working on a small solar and 12V battery system using a SmartSolar Charger, Phoenix Inverter, and SmartShunt. This is intended to be a solar power demonstration unit so it would be very helpful to measure irradiance and cell temperature with an IMT sensor and have a few Si-RS485TC-2T-v-MB available.

However, I am having trouble getting the sensor to connect properly. I am using the official FTDI USB-RS485-WE-5000-BT adapter as recommended and it can be seen and seems to connect for a couple seconds every minute or so but no readings show up. The sensor is powered directly from 12V battery voltage.

I had attempted this using a Raspberry Pi running Venus OS as described here: but have switched over to a Cerbo GX in order to attempt to rectify this problem with no change in the behavior.

Sensor shows up but shows "Not Connected":


Does seem to connect every ~1-2 minutes but nothing shows up:



I have no trouble accessing the sensor using Si Modbus Configurator from my PC and can read values from it. I do see the G value change when shining a light on it. Everything seems to be configured properly there according to and the IMT application note.



The VRM does show "Meteorological sensor [1] Product Id" to be b030 after connection but nothing else in the data export.

Pretty stumped as the device is seems to be recognized but not getting any data through. Any ideas to help me troubleshoot this?

VRMVenus OSVenus GX - VGXsensor
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1 Answer
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·


Firmware on the IMT sensor is too old. It has 1.51. It needs at least 1.52.

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tan-tonge avatar image tan-tonge commented ·
Really appreciate the quick support by your team on this issue! We are following up with IMT but might have to buy a new one
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israel-s avatar image israel-s commented ·

Is there a way or a new update that is compatible with imt sensors prior to FW 1.52 ?

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