User Guide

DigiTemp Digital Thermometer
Instruction Manual
Page 2
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Battery replacement
The instrument is powered by two alkaline manganese 1.5 volt cells, type LR6 (AA). When these are due for replacement the dis-
play will alternate between the temperature reading and message bAtt. This warning will be given when the battery voltage falls
to 2.0 volts (1.0 volt per cell), at which point the battery has approximately two months' life remaining. An internal voltage regula-
tor circuit maintains measurement accuracy until the battery voltage falls to approximately 1.5 volts. Always replace the cells in
pairs, do not mix old and new cells.
To replace the battery unscrew the front bezel ring and remove the window and sealing gasket. Remove the two nylon-headed
screws and lift off the dial. Remove the old cells and fit two "AA" size 1.5V alkaline manganese cells into the battery holder. The
correct polarity of the cells is shown in Figure 2 below and is also marked on the battery holder. (The instrument will not be dam-
aged if the cells are fitted incorrectly.) Refit the dial, place the sealing gasket on the front face of the case then centre the win-
dow on the gasket. Refit the bezel ring tightly with firm hand pressure.
Figure 2 - Correct battery polarity
Calibration
Each DigiTemp thermometer is fully calibrated during manufacture and certificates of calibration may be requested at time of
ordering. It is recommended that the calibration of the thermometer should be checked against a known temperature standard
every 12 months or at intervals specified by relevant quality assurance procedures. British Rototherm offers a rapid in-house
recalibration service for its temperature measurement products, traceable to national standards. Please contact the Sales Office
for details.
Procedure
Calibration of the DigiTemp thermometer is achieved by adjusting two multi-turn trimmer potentiometers which are located behind
the dial. One trimmer (P1) provides adjustment of the zero reading, a second (P2) controls the span.
An ice bath reference should be used when setting the zero trimmer to give a reading of 0°C (32°F) and the span adjustments
may be made by comparing the readings of the DigiTemp with those of an accurate reference standard thermometer at a higher
temperature. (For best accuracy the higher temperature should be close to the upper measurement limit.) If a standard ther-
mometer and high temperature bath are not available the DigiTemp may be checked by immersing the stem in boiling water
(100°C, 212°F).
1. Fully immerse the stem in a bath containing a mixture of clean crushed ice and water. Allow time for the stem to settle at
the temperature of the ice bath, stir the bath occasionally. Adjust the zero trimmer potentiometer if necessary until a
reading of 0.0°C is obtained (32.0°F for the °F version).
2. Transfer the stem to a high temperature calibration bath (e.g. 100°C) containing a reference thermometer if available.
The tip of the stem should be placed close to that of the reference. Allow sufficient time for the stem temperature to
reach that of the bath, then adjust the span trimmer potentiometer (P2) until the display reading matches the reference.
3. Return the DigiTemp stem to the ice bath and check that the 0°C reading has not altered. It may be necessary to repeat
the above zero and span adjustments several times until both readings are satisfactory.