Vaisala HMP228 - Manual (Page 44)

HMP228
Operating Manual
M210282en-A
38
4.8.1.3 Using LED commands
If both the analogue outputs and humidity/temperature channels are calibrated,
the analogue outputs should be calibrated first. This applies only when the
calibrations are made using the LED commands!
• connect an ammeter/voltmeter to the analogue outputs (connector X2)
• Give command ¡¡ll.
• the LED on the left flashes; set the low end of channel 1 with the ar-
row keys and press ENT
• the second LED from the left flashes; set the high end of channel 1
with the arrow keys and press ENT
• the LED on the left flashes; set the low end of channel 2 with the ar-
row keys and press ENT
• the second LED from the left flashes; set the high end of channel 2
with the arrow keys and press ENT
The analogue outputs are calibrated to ensure that outputs are correctly scaled:
for example, when the output is scaled to 4...20 mA, the low end of the scale
is 4 mA and high end 20 mA exactly. However, when 0... 20 mA output is
used, the output cannot be adjusted to exactly 0 mA, but to 50 µA. When 0...1
V, 0...5 V or 0...10 V output is in use, the output is adjusted to 50 mV. The
following table summarizes the correct output values.
Summary of the correct output values:
Output scale:
0...20 mA
4...20 mA 0...1 V 0...5 V 0...10 V
low end: 50 µA 4 mA 50 mV 50 mV 50 mV
high end: 20 mA 20 mA 1 V 5 V 10 V
4.9 Other functions
4.9.1 Adjusting the contrast of the display
The contrast of the display can be adjusted using the trimmer "LCD display
contrast" located next to the press switches.
4.9.2 Reverting to factory settings of the serial port
If the serial port settings are not known, no commands can be given via the
serial interface. The settings can be reverted to the factory settings by inserting
a jumper in connector X16. The jumper must be inserted when the power is
on!