Seaward DP6 - Manual (Page 18)

Operating Instructions Thermocouple Calibrator Type DP6
17
completion of the measure calibration, you will be given the choice of ending the
calibration routine or selecting the next option.
SOURCE: To calibrate the source mode, press the SRCE key and with a precision
digital voltmeter connected to the DP6 terminals, note the reading on the DVM. The
right hand display will indicate the value that the DP6 should be injecting. If the DVM
value is within the required tolerance, then press OK. If the value is outside the
tolerance, then press CAL. The display will ask you to enter the value as measured
on the DVM. Press OK and the DP6 will digitally correct its output and the DVM
should now measure the corrected output value. If you are satisfied with this
calibration point, then pressing OK moves on to the next calibration point. Repeat
this procedure for all the calibration points. After the last calibration the display will
return to the main calibration menu. At any time during the calibration procedure it
is possible to escape back to the main calibration menu by pressing the QUIT key.
RJ REFERENCE JUNCTION: This function is carefully set up during the final factory
calibration prior to dispatch and it is not normally recommended that this calibration
is readjusted unless the calibration laboratory is capable of sensing and measuring
temperature to an absolute uncertainty of better than 0.01 degrees Centigrade.
Should you consider it necessary to calibrate the Reference Junction then proceed
as follows. Press the RJ key and the right hand display will indicate the Reference
Junction temperature as measured by the internal sensor which is buried in a large
copper block mounted directly behind the input terminals. The option is then given
to accept this value or enter a new value.
To determine the temperature of the Reference Junction it is necessary to open the
DP6 case and insert a calibrated Pt100 sensor in the copper block behind the
terminals. The option is then given to accept this value or enter a new value.
To determine the temperature of the Reference Junction it is necessary to open the
DP6 case and insert a calibrated Pt100 sensor in the copper block behind the
terminals. A
1 ⁄
4
-inch hole is provided for this purpose. A few precautions are
necessary to achieve the best possible measurement performance. A contact
grease should be used to give good thermal contact; the instrument should be left
for at least 30 minutes after inserting the sensor and before measurement; the
measuring current to the standard sensor should be kept to a minimum and applied
only whilst a measurement is made and not left continuously powered. These
measures will avoid any errors due to self-heating of the sensor.
Measure and note the temperature of the copper reference block and press CAL.
The display now asks you to enter the Reference Junction temperature; pressing the
OK key accepts this value and the corrected RJ value is then indicated in the DP6
display. OK returns you to the main calibration menu.