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Analog Relay Mux Board
Example:
AD1200 card jumper set range of 0-10 Volts unipolar.
Gain of 1000 is selected for Channel 0
Ambient temperature of 18 degrees Centigrade
Thus CJC circuit gives a voltage of 18 x 0.5 mV = 9mV.
9mV input Channel 0 at gain of 1000 equivalent to 9 Volts
9 Volts on 0-10V i/p range is 9*4096/10= 3686= E66hex
To convert a reading into a temperature in degrees Centigrade
use the following formula:-
Temp in C = (ADC Reading * Input Span In Volts)
where the 0.5mV per degree C is 0.5/1000 Volts per degree C.
Thus for the above ADC reading of 3686 decimal, with a 10Volt
span in the input range and a Gain of 1000.
Temp in C=
Temp in C=
Calibrating The Cold Junction.
The cold junction compensation circuit can be calibrated simply
in the following manner. Place a precision voltmeter across the
CJC TO REL0 ENABLE jumper pins. Adjust potentiometer R23
with a screw driver so that the voltmeter reads 0.5mV times the
ambient temperature. Thus if the room temperature is 20 degree
C, R23 should be adjusted till the voltmeter reads exactly
10mVolts.
______________________________ _
(4096 * Gain * 0.5mV per C)
__________
( 3686 * 10)
(4096 * 1000 * 0.5/1000 )
_______
( 36860) =
(2048 )
18 degrees] Centigrade.
Reference
Page 9
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