Humidity Probes
Relative Humidity
Relative Humidity is defined as the ratio of the amount of gaseous water vapor present in the air compared to the total that could be present before condensation occurs. This condensation point is called
the Dew Point. RH is expressed as a percentage, where 100 percent represents the dew point, or point of maximum saturation.
Accuracy vs. Cost: There is a direct relationship between accuracy and cost. COS calibrates it’s probes using the ASTM E 104-85 method, which is based on primary standards. The two probes we offer are electrically identical; the difference is in the calibration. Our lower cost, “field” version is calibrated using a three point method, and is accurate to +/- 3 RH units. The higher cost “Lab” grade instrument is
calibrated using a seven point method, and is accurate to +/- 1 RH unit. Each calibration point requires a relatively long “settling” time (approximately 2 hours) to achieve equilibrium in the test environment. In general, the probes will reach +/- 3 % equilibrium with the test vapor in approximately 2 to 4 minutes. To reach +/-0.2% requires a much longer settling time. The greater the accuracy desired, the longer it
takes to calibrate.
COS manufactures two versions of RH instruments. These low cost, rugged and reliable instruments provide a 0-5 volt
output in response to RH between 0 and 100 %. Our probes use a capacitive probe to sense RH, which we have found to be superior to the resistive versions for most industrial type applications in corrosive environments. Our probes are packaged in a metal, 1 inch diameter probe body with a protective shield over the probe itself.
the Dew Point. RH is expressed as a percentage, where 100 percent represents the dew point, or point of maximum saturation.
Accuracy vs. Cost: There is a direct relationship between accuracy and cost. COS calibrates it’s probes using the ASTM E 104-85 method, which is based on primary standards. The two probes we offer are electrically identical; the difference is in the calibration. Our lower cost, “field” version is calibrated using a three point method, and is accurate to +/- 3 RH units. The higher cost “Lab” grade instrument is
calibrated using a seven point method, and is accurate to +/- 1 RH unit. Each calibration point requires a relatively long “settling” time (approximately 2 hours) to achieve equilibrium in the test environment. In general, the probes will reach +/- 3 % equilibrium with the test vapor in approximately 2 to 4 minutes. To reach +/-0.2% requires a much longer settling time. The greater the accuracy desired, the longer it
takes to calibrate.
COS manufactures two versions of RH instruments. These low cost, rugged and reliable instruments provide a 0-5 volt
output in response to RH between 0 and 100 %. Our probes use a capacitive probe to sense RH, which we have found to be superior to the resistive versions for most industrial type applications in corrosive environments. Our probes are packaged in a metal, 1 inch diameter probe body with a protective shield over the probe itself.
COS Model CRH201D-3: 3% RH probe, 10 to 90%RH...........................200-40200-01
COS Model CRH201D-1: 1% RH Probe, 10 to 90%RH...........................200-40200-02
COS Model CRH201D-1: 1% RH Probe, 10 to 90%RH...........................200-40200-02
Part Number
COS
We also recommend the EE Electronic Probes, model EE08-PFTZV11D6HC01/T79 Range 0-5V=0-100% RH, -40 to +100 degrees C built in temp probes.