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A friend came to me with a curious problem regarding the research weather stations he maintains. The Geonor rain gauges were experiencing glitches. Some of his stations exhibited only occasional problems, and others were failing almost daily.

In the plot below, the rain gauge output is in blue. It should be a steady, increasing line representing the weight of the accumulated precipitation. The green line is the battery voltage. In this case, when the sun would hit the solar panels each day, the solar charge controller turned on and the rain gauge stopped working.
Rain gauge output in blue. Solar panel output in green.

I found that the systems he maintains use a Morningstar Sunsaver solar charge controller. These solar charge controllers use a PWM output to charge the battery. This means that rather than just regulating the voltage and current to the battery, the controllers switch the charge voltage on and off very fast. This type of electrical signal can cause electrical noise and interfere with other devices on the circuit. Depending on the lengths of wires to the batteries and the susceptibility of other systems, the noise may become significant.

The Solution

After some testing, it was demonstrated that the PWM power from the solar charge controller was interfering with the vibrating wire signal adapter of the Geonor rain gauge. Adding a 12 VDC linear regulator to the circuit resolved the problem.

We quickly created a new product to address this problem. The regulator is now available as Dyacon RLP‑2WTM.

With an input range of 12.5 V to 36 V, RLP‑2W is also suitable for industrial automation applications. The On/Off control input of RLP‑2W allows for power optimization using a digital signal to control the regulator output.

Let us know if you have a specific problem with your data acquisition system. We’d love to see if we could help.