18
Chapter 1 TriLog
1.3.
Sensor Calibration
In this chapter you will learn how to increase the TriLog system accuracy using
calibration. Most of the sensors are linear, i.e. the output level of each sensor
changes according to the equation:
b
aX
Y
+
=
Where:
Y
–
The sensor
’
s output (voltage level varying from 0 to 5V)
X
–
The sensor
’
s input
a
–
The sensor
’
s gain
b
–
The sensor
’
s offset
The calibration process allows us to control the offset, and in some cases even the
gain, of a sensor. The TriLog system offers 4 types of calibration:
1. Hardware offset calibration.
2. TriLog automatic zero calibration.
3. MultiLab
“
Sensor calibration
”
.
4. Factory calibration (no manual calibration required).
1.3.1.
Hardware Offset Calibration
On some of the sensors there is a screw controlling the sensor offset. To calibrate
the sensor, rotate this screw until the sensor shows the correct measured value
(obtain the actual "correct value" from another source that is known to be accurate).
1.3.2.
TriLog Automatic Zero Calibration
TriLog is able to automatically calibrate the sensor offset for all analog sensors
accurately, quickly, and for every new experiment conducted.
The calibration method is very simple. Whenever you plug in a sensor, the data
logger checks to see if the selected sensor measures a value within
±
2% of its
“
zero
value
”
. If so, TriLog sets that value as zero.
1) To enable this feature, make sure that the sensors are at their
“
zero values
”
when you plug them in. To ensure the most accurate
“
zero value
”
: Shorten the
Voltage sensor plugs.
2) Leave the Current sensor plugs open.
3) Cover the Light, Photo-Gate, and Microphone sensors.
4) Insert the pH sensor in a pH-7.0 solution.
5) Unload the Force Transducer.
6) Place the Accelerometer on a stationary surface.
7) Place the Temperature probes in ice water.
8) Place the Pressure sensor in a 1 ATM (1013 mb) Chamber.