Rense Instruments” S-503 relative humidity generator/calibrator can generate and hold RH values from 10-90 percent in 0.1 percent RH steps. The unit stabilizes to within 0.5 percent RH of the set point in about 10 minutes and has ports to test up to seven RH transmitters simultaneously. All models are CE marked. The system is equipped with the convenience of a 15 Vdc supply to power units-under-test. A built-in LCD shows actual chamber RH and temperature, as well as the RH signals from the test units. A selector switch permits testing of transmitters with the most popular analog output formats, including zero to one, zero to five, and zero to 10 Vdc, and four to 20 mA current loop. While intended for laboratory use, at about 3.5 lbs the S-503 is small and light enough to be portable. Available as a standalone instrument or as a kit with carrying case and accessories, the S-503 is a good fit for those needing a way to perform basic RH calibrations at a fraction of the cost of other test chambers.