Oakton WD-08369-70 - Minidrum Hygrothermograph

The Oakton WD-08369-70 minidrum hygrothermograph is a benchtop unit that has a seven-day (172-hour) rotation for humidity and temperature recordings, a quartz-controlled drive for constant drum rotation, and an aged bimetallic strip temperature sensor for accurate temperature readings. Hygrothermographs are used to measure and document humidity and temperature over time in computer rooms, greenhouses, food storage rooms, warehouses, museums, and in quality control (QC) laboratories, education and research lab testing environments.

This hygrothermograph’s quartz-controlled drive system allows a steady chart speed, even when the battery or spring-wound system begins to run down, which keeps the chart running for seven days. An aged bimetallic strip temperature sensor provides accurate pressure readings. A human hair bundle relative humidity (RH) sensor provides ambient humidity measurements with accurate linearity, repeatability, and temperature compensation.

This unit has a protective acrylic cover that locks into place for security. Its cover is lightweight and corrosion-resistant, and a sturdy metal base provides a range of use in indoor and sheltered outdoor environments. The minidrum hygrothermograph comes with one sheet of pre-attached chart paper, one red cartridge pen, and one blue cartridge pen. Exposure to RH levels above 90% can cause a decrease of about 7-10% RH in readings over the entire range due to temporary elongation of the hair bundle. When exposed to humidity levels below 80%, hair bundle will return to normal in about three weeks. The 08369-70 is factory preset for a seven-day rotation. The response time is fifteen minutes for 45% of reading.

Thank you for selecting an OAKTON thermohygrometer. These precision instruments are useful for monitoring temperature and relative humidity conditions over time. They create a permanent chart recording of these measurements for your records. Their quartz-controlled drive maintains an even drum speed even when batteries are weak (or when the spring winding runs down).

Typical applications include general weather measurements, agriculture, horticulture, monitoring the condition of test laboratories, humidity chambers, computer rooms, precision machinery rooms, food storage facilities, warehouses, museums, bank vaults, film and book storage facilities.

You have one of five available models:

Changing Drum Rotation Length

NOTE: Minidrum models 08369-50 and 08369-70 operate on a 7 day rotation only.

Long cycle model 37250-20 accepts either 1 month or 3 month chart rolls-it is not necessary to adjust drum speed.

Spring wound, two speed hygrothermograph 37250-10

This model lets you select between a 1, 7, and 32 day drum rotation. When you receive your hygrothermograph from the factory, it is set for a 7 day rotation. See figure D

IMPORTANT: make sure you have the appropriate chart paper for the rotation speed you select.

1. Look at the bottom of the cylinder drum. You will see notches for two gears. Only one gear will be in place. See figure A
2. The alternate gear is located on a post at the corner of the thermohygrometer’s base. Remove it from the post. See figure B
3. Using two screwdrivers, lift the gear currently installed on the bottom of the cylinder drum. See figure C
4. Insert the other gear onto the opposite shaft on the bottom of the drum.
   • The one-day gear slides on the shaft marked “24 H / Z = 22”. This gear has 22 teeth and a larger diameter than the 7-day gear.
   • The seven day gear slides onto the shaft marked 168H / Z = 18. This gear has 18 teeth.
5. Place the gear not in use over the post at the corner of the thermohygrometer’s base for storage.
6. Install the cylinder drum onto the cylinder shaft.

Three speed hygrothermograph 37250-00

This model lets you select between a 1, 7, and 32 day drum rotation. When you receive your hygrothermograph from the factory, it is set for a 7 day rotation. See figure D

IMPORTANT: make sure you have the appropriate chart paper for the rotation speed you select. See page 26 to order more chart paper.

1. To switch from 7 day operation to 1 day operation, flip the switch on top of the cylinder drum to 1D. See figure E
2. To switch from 7 day operation to 32 day operation, flip the switch on top of the cylinder drum to 32D. See figure F

Installing Optional Axial Fan

NOTE: The axial fan is not for use with minidrum models 08369-50 and 08369-70. The external draft fan (optional) attaches to the protective cover. It improves instrument response and accuracy by directly pulling surrounding air into the instrument. Use the fan in areas where ventilation is poor.

To attach the fan:

1. Install the fan on the single column of five vents located on the protective cover. See figure A
2. Position fan so that the spring clips on the fan go into the upper vent slots on the hygrothermograph cover. See figure B
3. Let the fan slide down until it stops. Make sure both spring clips are fully engaged in the cover. See figure C
4. Position the instrument so the flow of air from the fan will not be blocked.
5. Plug the power cord into an 110 to 120 volt, 50/60 Hz outlet. For 220 V operation, order optional 220 V transformer (sold separately in “Accessories”).