Dickson THDx Manual - Page 4

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Operating Information

Pens

The blue pen has a longer pen arm and records humidity

or dew point (depending on your dip switch selection,

see pg. 6). The red pan has a shorter arm and records

temperature. The pens are offset to allow the red pen to

glide under the blue pen. The blue pen indicates the cor-

rect time and the red pen precedes it by 3/16 of an inch.

The pens move in increments across the chart as

sensor readings change. The display provides smoother

and faster readings than the pens. At any given time

there may be a slight discrepancy in the position of the

pen and the reading on the display due to hysteresis.

For visual spot checks the display is more accurate

than the pen position but both are within the stated

specifications of the unit (see "Specifications" on pg. 2).

Pen Adjust

Pen adjustment may be needed if the pens and display do

not match exactly.

1. Make sure the pen lifting bar is lowered and press

the "Pen Home" key.

2. Turn the chart hub clockwise, rotating the chart

3. With a small screwdriver loosen the pen adjust

screw on the pen arms and adjust the pen tips to

the outer most circle on the chart.

4. Retighten the screws. After pressing "Pen Home"

again the pens should now read correctly with the

display.

Probe

The THDx probe sits in the cradle in the back of the unit.

The THDx probe comes with the standard 8" cord. An

extension cord can be ordered to allow for remote sens-

ing capabilities.

Display Symbols

��

Alarm is on.

Cord Installation

If you have ordered an extension cord for remote sensing

capabilities follow the instructions for cord installation

listed below.

1. Turn the unit upside down or on its side so that you

2. Twist and pull the black rubber strain relief,

3. Slide the strain relief on the cord

4. Inside you will see a standard connector which

5. Remove wand from cradle by sliding upward.

6. Return the wand to the cradle mounted position by

Power Supply

We recommend using AC power with four "D" batteries

installed as a back-up power source. This ensures that

your recording will not be interrupted when there is a

power failure. When the instrument is using battery

power, the unit will update very slowly to extend battery

life. The 120V AC adapter plugs into the back of the

recorder beneath the probe cradle.

Lo Batt: Low battery indicator

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UC: the unit is in "User Calibration" mode. This is dis-

played in the upper right hand corner of the display.

Reading Update Indicator: These rectangles will flash

along the bottom of the display as long as the recorder is

taking readings. If you are using batteries as the power

source the update indicator rectangles will still flash but

the rate will be very slow in some modes and "B" will

light on display. The rectangle furthest to the right is lit

continuously when the unit is using battery power.

MIN: This symbol is displayed when you are setting a

maximum alarm or when you have pressed the "MIN/

MAX" key and the maximum value is being displayed.

MAX: This symbol is displayed when you are setting a

Figure 4

minimum alarm or when you have pressed the "MIN/

MAX" key and the maximum value it being displayed.

can see where the probe connects to the back of

THDx.

beginning on the back of the recorder body (see

"Instrument Anatomy" on pg. 3).

looks like a phone jack. Using a small screwdriver,

press retention tab and the connector will pop out

easily.

Repeat steps 1 through 3 for the portion of the cord

that connects to the wand.

sliding the wand down into the cradle until it fits

into the grips. The probe can also be replaced by

positioning it in back of the cradle area pressing it

into the cradle until it snaps in place.