Sierra Wireless MP 875, User Manual

Page: 48 / 68

MP 875 Modem User Guide
Analog input setup
The Analog Input window (
Tools > Options > MP > Input/Output
)
is used to configure devices on the four analog inputs. Each tab
corresponds to a pin:
Analog Tab Connector Pin
Input 1 14
Input 2 7
Input 3 15
Input 4 8
To configure an analog sensor or gauge, select the tab that
corresponds to the pin you are using and complete the fields as
follows:
• Label: Enter a description of the sensor or gauge (
Measured
Voltage
,
Vehicle Speed
, etc.), up to 20 characters long.
• Raw value: Shows the analog value from the input (read­
only). The analog input has a 10-bit (1024-step) resolution,
so the raw value range is between 0 and 1023.
• Zero scale: Enter the minimum value for the units you are
reporting (used to convert the raw analog value of zero).
• Full scale: Enter the maximum value for the units you are
reporting (used to convert the raw value of 1023).
• Current value: Shows the resulting converted value using
the zero and full scales entered.
• Unit: Specify the units of the input (
volts
,
km/h
, etc.), up to
20 characters long.
Example
If you are measuring temperature, and the thermometer you
have connected to the I/O connector measures between -30
(raw value 0) and +50 (raw value 1023) degrees Celsius, then
your zero scale is
-30.0
and your full scale is
50.0
. Your label
could be
“Temperature
”, and units,
“degrees C”
.
The measurements are calculated for the 80-degree range
(between -30 and +50), which is divided into 1024 steps
(0.0781 degrees per unit step). A reading of 25 degrees
(55 degrees above the minimum) would therefore show a raw
value of 704 (55 degrees/0.0781 degrees per unit).
48 2130808