The Arten Meter features a user-friendly design while the small size, reliability and accuracy of the Thermohygrometer has made it popular with museums internationally.

The meter is ideal for use in exhibit cases and microclimate boxes where a low profile is desirable.

The humidity indicator strip on the lower portion of the meter reads from 15% to 75% relative humidity (RH). This provides an independent reading to verify that the meter is properly calibrated. When looking at the humidity indicator strip find the square that looks closest to neutral grey (you can compare with the background color of the meter). You may find this point lies between two squares. In the image above this would be between the 55% and 65% squares. The meter is easy to re-calibrate and is available with temperature measurement in either Fahrenheit or Centigrade.

Dimensions:
2.8 cm H x 4.8 cm W x 1.4 cm D
(1.1" H x 1.9" W x 0.55" D)

Calibration Kit
The Thermohygrometer humidity calibration kit consists of 5 sets of Ziploc polyethylene bags and packets of silica gel conditioned 50% specific relative humidity (�2%). Place the meter in the Ziploc bag with the calibration packet, seal the bag and wait one hour for the system to reach equilibrium. If the meter reading is different, pierce the back of the bag with a screwdriver, and adjust the meter. Reseal the hole with tape, wait 15 minutes, and then recheck and repeat the process if necessary. This procedure should permit an accurate calibration to within 1-2% of the RH indicated on the silica gel packet. Because of the limited buffering capacity of the individual silica gel packets and the moisture permeability of the Ziploc bag, it is not advisable to reuse individual calibration kits.

A psychrometer is an essential piece of equipment for the calibration of hygrothermographs and other temperature and relative humidity monitoring devices. The Psychrodyne Electronic Psychrometer is included in our product line because of its accuracy and ease of operation.

Relative humidity is calculated by comparing the drop in temperature due to the evaporative cooling effect of the wet bulb thermometer in relation to the dry bulb thermometer. To operate, moisten the wick with distilled water, and turn the unit on. An electric fan draws air across the wick of the wet bulb thermometer. Leave 2-5 minutes for the unit to equilibrate. Once the wet bulb reading stabilizes, relative humidity is easily determined from the look-up table.

Isuzu Hygrothermograph TH27R

Hygrothermographs continuously record temperature and relative humidity in interior spaces. Temperature and humidity are tracked on a chart attached to a rotating drum.

The Isuzu hygrothermograph utilizes a precision quartz clock drum. The new Isuzu models TH25R and TH27R now house the clock mechanism and batteries in the drum, which allows for easier maintenance and greater reliability. The bimetallic element and calibrated hair bundle measure and record constantly changing temperature and relative humidity conditions in the room, providing a continuous recording of space conditions. The Isuzu hygrothermograph provides many years of reliable service when properly maintained.

Most RH meters and recorders do not directly measure RH, but rather, they measure a "secondary" response to changes in RH and require periodic calibration. Psychrometers, which are considered to be "primary" devices, are used to calibrate other humidity monitoring equipment. We recommend that hygrothermographs, RH data loggers and thermohygrometers be checked periodically with a calibration device such as a psychrometer to ensure accuracy.

Two models are available

Model TH25R
black, rectangular
(replaces the 3126).

Model TH27R
white, curvilinear
(replaces the 3128).

Each unit comes with a one-year supply of either 7-day or 31-day charts (please specify) and runs on 2 C batteries.

TH27R
36.1 cm W x 15.0 cm D x 28.7 cm H
(14.2" W x 5.9" D x 11.3" H)