Wireless Contact Closure Sensor

Having trouble communicating with wireless senors. Sensors respond perfectly when near base station/modem. But lose communication with node red once move to their designated location.

does it work with alpha station if you move it away and whats the distance between sensor and modem when it quits ?

Yes it works with alpha station and node red. Then once its moved to the designated truck we lose communication with it. Sometime replacing the antennas work but sometimes it does not. The environment in which we use them is pretty harsh and antennas breaking is not uncommon. we are just trying to figure out a solution. at this rate we will be spending a fortune on antennas, as we have over 100 sensors

the furthest distance is less than 300 ft. The closest could be as little as 20 ft


our sensors go on each one of these trucks to monitor fuel levels

Have you tried mounting the 900 mhz antennas to the outside of the trucks? You might be able to find an outdoor rated omni directional antenna that could be mounted to the exterior of the truck.

The sensors and modem do use Mesh transceiver modules(Digi Mesh) however keep in mind that the battery powered wireless sensors you install in the trucks go to sleep when they are not transmitting information so they cannot relay wireless transmissions because they are asleep. You could however mount stationary full time powered router boxes in different areas of the lot to strengthen network integrity. For these router devices you can just use a modem like this:

Just power it up and it will retransmit any wireless signals it receives which may bridge the gap between the sensors and your modem.

Ok. We do currently mount sensors on the outside.

The first thing I would try is a high gain antenna on the modem. This may be enough to solve the issue. We do not carry these antennas but there are many suppliers of 900 mhz antennas which should work. Just make sure you can terminate the antenna to the RP-SMA connection on the modem.

If that does not work then I would try adding a few Modems linked above to act as repeater devices through the lot.

Ok our modem is currently located in a control room connected to our PC which runs our node red software as well as alpha station. we have the antenna and cable ran to the top of our unit which is 10 feet high. that height is lower than most of the obstructions. could increasing the height of the antenna also help?

The problem with the antennas is the environment in which they are used is pretty harsh so we are seeing not only damage but lost antennas. Just looking for a solution to minimize this. Since we have over 100 sensors this could get to be very expensive. Do you know of any other antenna types that would be more durable/ smaller and less likely to break or be damaged.

if the antenna extension cable is too long it will reduce the signal strength as well. try to keep the antenna extension cables as short as possible.

as Travis mentioned install a repeater between the sensor and the modem and that should take care of the lost packets.

high gain antenna

make sure the modem and sensor RF power is set to 4. You can use alpha station to check the RF level.