Rosemount Analytical's Latest Relative Humidity Sensor Line Sets New Accuracy Standard

Rosemount Analytical, Uniloc Division, has released Hygrodat 10 and 20 relative humidity sensors. The new series, which is targeted specifically for the food, pharmaceutical, and semiconductor markets, sets a new accuracy standard of ±1% over the entire 0 to 50°C temperature range. By increasing the accuracy in measuring relative humidity, the Hygrodat allows the user to validate strict relative humidity operational protocols (OP's), save on heat losses to air propellants, and reduce process shutdown.

A micro-controller ensures easy operation by means of a display (Hygrodat 20) or LED indicators (Hygrodat 10). With the press of a button, the electronically controlled calibration is performed. Up to five points can be calibrated with the user-friendly system: diodes as well as an LCD display walk the user through the process. The micro-controller also constantly monitors the instrument during operation so that maintenance is automated.

Three mounting options are available. Independent mounting of the transmitter and sensor facilitate remote measurement. With this mounting option, the sensor and transmitter are connected by a cable that can reach up to 60 m without an amplifier. Wall mounting is available for ambient measurement. Duct measurement is easily accomplished with flange mounting.

Due to the standardized DIN-rail or flange-mounted sets, the Hygrodat can be installed quickly and easily. The sensitive electronics of the transmitter are housed in a removable lid. This allows the base of the housing to be mounted without risk of damage to the electronics. The sensor and transmitter are connected by a cable that can reach up to 60 m without an amplifier.

The measuring element of all Hygroline humidity sensors is based on the electrolytic cell. This device uses a thin film of a special hygroscopic electrolyte mounted between two electrodes. The electrolyte changes its electrical impedance in response to very small changes in water vapor pressure. This change is measured by the instrument and interpreted as relative humidity. The steep impedance change (approximately 1000:1 over the measuring range) allows the sensor to be mounted on cables as long as 60 m without the need for a preamplifier.


Humidity Measurement:

Measuring Range:

6 to 100%


5-point calibration at 25°C: ±0.5%

5-point calibration at 0 to 50°C: ±1%

without calibration: ±2%


<0.3% rH

Long-term stability under typical conditions/year:

<1% rH

Temperature Measurement:

Measuring Range:

-20 to 80ºC


±0.5 K


<0.1 K

Operating Temperature:

controller box: -10 to 50ºC

sensor: -20 to 60ºC

Storage Temperature:

-20 to 60ºC

Electromagnetic Compability:


EN 50081-2


EN 61000-3-2/-3


EN 50082-1/-2

Power Supply:


90 to 260 V


9 to 35 V

Output Signals:


0 to 1 V, 0 to 10 V


0 to 20 mA, 4 to 20 mA


External loads to ground (Voltage output):

>8000 Ohm

External loads (Current output):

<500 Ohm

The Uniloc Division is one of the three companies that form Rosemount Analytical Inc., a division of Fisher-Rosemount. The Uniloc Division designs and manufactures refractometers, analyzers, transmitters, and sensors for the online measurement of pH, ORP, conductivity, dissolved oxygen, dissolved carbon dioxide, chlorine, ozone, and turbidity.

For more information, contact Rosemount Analytical Inc., 2400 Barranca Parkway, Irvine, CA 92606. Tel: 949-863-1181; Fax: 949-474-7250.