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This product has been replaced by the TH8P3

Our THDX has been completely redesigned and now goes by Model TH8. The new TH8 has the same functionality as the THDX but in a smaller, more robust package.

Click on the link to view and order the NEW TH8 Chart Recorder.

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Important Information

Charts are sold separately.

Dickson Expert Services

Our Dickson Data Division has specially trained representatives to address the needs of customers with large installations or unique demands. Please call 888-452-4626.


D Cell Battery

C415 8" (203mm) Chart 24-Hour, -20 to 120 F $54.00 Add
C417 8" (203mm) Chart 7-Day, -20 to 120 F $54.00 Add
C472 8" (203mm) Chart 24-Hour, -20 to 50 C $54.00 Add
C473 8" (203mm) Chart 7-Day, -20 to 50 C $54.00 Add
C476 8" (203mm) Chart 24-Hour, 40 to 110 F $54.00 Add
C477 8" (203mm) Chart 7-Day, 40 to 110 F $54.00 Add
C478 8" (203mm) Chart 24-Hour, 5 to 40 C $54.00 Add
C479 8" (203mm) Chart 7-Day, 5 to 40 C $54.00 Add
C480 8" (203mm) Chart 31-Day, -20 to 120 F $54.00 Add
C481 8" (203mm) Chart 31-Day, 40 to 110 F $54.00 Add
C482 8" (203mm) Chart 31-Day, -20 to 50 C $54.00 Add
C483 8" (203mm) Chart 31-Day, 5 to 40 C $54.00 Add
P246 3 Red, 3 Blue Pens $58.00 Add

Frequently Asked Questions

  • The Humidity sensor has possibly been saturated or damaged.
  • If 99% is caused by the environment, this means that the sensor has been saturated. The THDX is not intended for condensing environments or applications over 95% however, a protective filter may be used (#A867) in some cases.
  • If the sensor was saturated, the unit may return to normal operation after a few hours in a dry environment.

Are there batteries in the Chart Recorder?

Are the batteries in correctly?

If there was momentary power outage (Brown out), the unit may not have had enough time to recognize this and switch to battery mode. (The unit may "lock up" or shut off in this situation)

Is the Chart Recorder locked up? This can be determined by taking notice of the cursor on the bottom of the display moving back and forth. If it's not moving, press the up arrow button. If it starts to move after the arrow button was pressed, then that confirms that the unit is in battery mode, in which case the unit will only update periodically to preserve battery life. So, if changes occur between updates, the unit won't capture and record those changes. (Very important draw back for battery mode)

If the cursor does not start to move after the arrow button is pressed, then the unit is locked up. This is usually caused by an interruption in power, in which case the Chart Recorder will not operate at all. To correct this, simply remove batteries and transformer, wait about 1-minute and power back up. This does not affect the units' functionality or calibration in any way.

Make sure that dip switch # 7 is off; this switch controls the display.

Make sure dip switch # 8 is off; this switch locks out the keypad.

Remove all batteries and adapter; wait about 1-minute to let the unit discharge. The unit should respond when the adapter is plugged back up.

Is the proper power adapter being used? It should be 6-Volts 700-800 milliamps.

  • Dip switches set for a specific range, but using chart for another range, or vice versa
  • Dip switch #3 (Celsius setting) is on, but using Fahrenheit chart, or vice versa
  • Pen(s) not inserted on pen arm(s) all the way
  • Pen home not set properly. Perform a pen home check by pressing the PEN HOME key, and verify the pen(s) stop at the maximum Temperature line on the chart. If the pen(s) don't line up, loosen the screws at the top of the pen arm(s), then adjust the pen(s) so that they are lined up properly. Then re-tighten the screw(s) on the pen arm(s)
  • Gears jammed or slipping (You should hear the gears grinding)