Vaisala DMP248, Operating Manual

Page: 73 / 141

C
HAPTER
7 ____________________________________________________________MAINTENANCE
V
AISALA
_________________________________________________________________________ 69
Adjustment using serial commands
Give command CT and enter the first point value and press <cr>:
>CT <cr>
'C : xx.x Ref1 ? yy.y <cr>
Press any key when ready
Set the Pt 100 simulator at the highest temperature to be calibrated,
and press any key. Enter the second point (gain) reference reading. If
second reference is not needed, press <cr> to complete one point
offset correction.
Adjustment using display commands
Select
Cali
in the main menu and then
T
; select two-point calibration
T
2 point cal
. Change the first point reading with the arrow keys and
press ENT.
Set the Pt 100 simulator at the highest temperature to be calibrated,
and adjust the second point (gain) to the reference reading.
Adjustment using LED commands
Connect an ammeter/voltmeter to the analogue outputs (connector
X2). Give command
¡¡l¡
, and adjust the first point (offset) with
the arrow switches to the same reading with the reference and press
ENT switch.
Set the Pt 100 simulator at the highest temperature to be calibrated,
and adjust the second point (gain) to the reference reading. If there is
no second reference, press ENT to complete one point offset
correction.
Disconnect the Pt 100 simulator and reconnect the Pt 100 wires to
solder lugs TP5, TP6 and TP7.
The correct connections according to the wire colours are:
TP5 TP6 TP7 TP8
blue green yellow black
If there is not a Pt 100 simulator available, the adjustment can be
made with two resistors of 84
Ω
and 154
Ω
whose resistance is known
precisely. Measure the resistor with a resistance meter. Look up the
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