Relative humidity sensor technology has many advantages over traditional titration methods, making it an ideal choice for companies who want to make quality products as efficiently as possible, but without the recurring costs of chemicals, glassware or disposal.

Now ABLE Instruments & Controls has won approval and conformity of its Computrac Vapor Pro moisture analyser to ASTM method D7191-05. A fast, easy, cost-effective alternative to titration methods, such instruments are durable enough for the production floor yet versatile enough for the laboratory (Fig.1). They require very little training to use accurately; even an inexperienced operator can produce reliable results.

“Many of our customers in the plastics industry have been looking for a reagent-free,
ASTM method that would allow them to quickly and easily test for moisture in their raw materials and finished products,” said Dave Quelch, senior product manager. “A task group was initiated to develop a moisture-specific method based on the relative humidity detection technology to provide a safe and cost-effective alternative for testing moisture content in plastics.”

The company has also introduced two additions to its family of moisture and humidity measurement instrumentation: the DT-20 dew point transmitter; SADP-Mini handheld dew point hygrometer and the bench top/portable CMH series of chilled mirror hygrometers.

The DT-20 is a two-wire loop powered dew point transmitter providing a 4-2mA output. It is available in the following measurement ranges:
-65°C to 2°C; -80°C to 20°C and -110°C to -20°C dew point and has an accuracy of ±2°C dew point. It is supplied with a NPL or NIST traceable calibration. Accessories include a local loop powered display and a panel mountable analyser/power supply.

The hand held SADP-Mini hygrometer can be used to verify installed transmitters such as the DT-20 transmitters or for tasks such as spot checks on gas supplies. This hygrometer has the option of onboard data logging (downloadable via RS485 or USB) and/or a 4–20mA output for use with a standalone recorder. Measurement ranges are as for the DT-20 and in addition -100 to 0°C and -80 to 0°C dew point. Pressure corrected readings are available through the integral calculator (just enter the gauge pressure of the gas). A field carry case is also available.

Finally there are the CMH chilled mirror hygrometers. The three enclosure variants (bench top/rack or panel mount, wall mount and portable) are available with three parameter options – dew point only, dew point, temperature and relative humidity, dew point and pressure and for a complete system, one of five sensor options: flow-through (1–3 stages) or insertion (one or two stages). Each hygrometer has scalable voltage and current outputs, in addition to a RS232 serial port.

Michell acquires Rense

Meanwhile, Michell Instruments now offers a range of relative humidity sensors, transmitters, hand-held instruments and humidity sensor calibrators, adding to its existing line of dew-point hygrometers and moisture analysers.

Michell’s group of international companies has acquired the Dutch relative humidity instrumentation manufacturer Rense Instruments. Rense products will be marketed and sold worldwide through the Michell seven sales and service centres and through a network of fully-trained exclusive distributors.

Established in 1974, Rense Instruments has developed a reputation for the design and manufacture of high quality, but low cost relative humidity instrumentation.

The product range is comprehensive, providing cost-effective solutions for almost any relative humidity application.

The line-up includes low cost wall-mounted humidistats, hand-held RH meters and industrial relative humidity sensors, probes and transmitters. Additionally, Rense manufactures a range of relative humidity calibrators that complements the Michell existing line of dew-point and humidity calibration systems.

The Rense product line is based on a highly accurate and stable polymer film relative humidity sensor that is calibrated in-house by systems traceable to international standards.

The sensor provides very fast response over a wide humidity range and is suitable for use in many air and gas environments.

Various physical configurations are available, ranging from a plastic wall-mount housing for room humidity control applications, through probe-type sensors for hand-held and chamber measurements, to stainless steel flange and duct-mounting transmitters for process humidity measurements.

All instruments are available with relative humidity only, or relative humidity plus temperature measurement.