For many years, Campbell Scientific has offered the HMP45C as our higher-accuracy temperature and relative-humidity probe. With the retirement of the HMP45C (due to part obsolescence), our goal was to find an appropriate replacement that would minimize the difficulties that can surface when replacing one sensor with another—a replacement in fit, form, and function.

Our search led us to the HC2S3, manufactured by Rotronic Instrument Corp. The HC2S3 offers comparable accuracy to the HMP45C at a reduced price. The HC2S3 also has similar wiring and programming, and is housed in the same 41003-5 10-plate radiation shield (with included hex plug) as the HMP45C.

The HC2S3 uses Rotronic's IN1 capacitive sensor to measure relative humidity and a 100 ohm PRT to measure temperature. It includes a polyethylene filter that protects the capacitive sensor from fine dust and particles and minimizes water absorption and retention. Alternatively, a Teflon filter is available for marine environments.

Although the HMP45C is no longer available, we will still recalibrate existing probes through our standard RMA procedure.