Transmission failure in remote PM sensor

I have a NCD wireless particulate matter sensor and a USM modem that I need to link into an existing remote monitoring application. I am reading the API packets that get transmitted every 30 seconds and the data seems fine. After about 24 hours, the modem no longer receives data and I have to carry out a manual reset. The battery voltage is 2.96 Volts, so I assume that there is enough power.
Is there a sleep setting which turns off transmission after a set time?

This sensor consumes a lot of power and i will NOT recommend using at 30sec interval.
If you want to use it wat 30 sec interval than use with external power.

I will reduce the transmission interval and use external power.
What is the external input voltage, it is not marked.

The recommended voltage is 12V

Thanks for that, Anil

As you have suggested, I have increased the transmission interval from 30 seconds to 30 minutes and powered the sensor from an external 12 V source. When I press the reset button on the sensor, I get a transmission, but after that, nothing. On the one transmission, the battery voltage was 2.88 V. Does this mean that it is still trying to get power from the internal batteries?

did you switch the power switch to external power position ?

I only know about the on-off switch. Where is the external power switch?
Is there a manual that I am missing?

yes the on off switch… its its in off position it will use external power.