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Page 3 of 97
Issue: 1.04
4
CONNECTING THERMOMETER SENSORS ................................. 43
4.1
The “Cable-Pod” Connectors ........................................................................................... 43
4.2
Connecting PRTs (4-wire) ................................................................................................. 43
4.3
Connecting PRTs (3-wire) ................................................................................................. 44
4.4
Connecting PRTs (2-wire) ................................................................................................. 44
4.5
Connecting Thermocouples (external Ice Point or WTP) .............................................. 45
4.6
Connecting Thermocouples (using RJ compensation) ................................................... 46
4.7
Connecting Thermistors .................................................................................................... 46
5
GOOD PRACTICE GUIDELINES .................................................... 48
5.1
Looking After Your microK ............................................................................................. 48
5.2
Making a Good Electrical Measurement ......................................................................... 48
6
THE MICROK TECHNOLOGY ........................................................ 51
6.1
The ADC ............................................................................................................................. 51
6.2
Substitution Topology ....................................................................................................... 53
6.3
Minimising Thermal EMFs .............................................................................................. 55
6.4
Solid-State Switching ......................................................................................................... 56
6.5
Inherent Stability ............................................................................................................... 56
6.6
Eliminating Self-Heating Effects ...................................................................................... 57
7
CALIBRATION ................................................................................ 58
7.1
Checking Calibration ........................................................................................................ 58
7.1.1
Checking the Master Current Source ..............................................58
7.1.2
Resistance Measurements ..............................................................59
7.1.2.1
Zero Ohms Check ..................................................................59
7.1.2.2
400
Ω
Internal Reference Resistor..........................................60
7.1.2.3
100
Ω
Internal Reference Resistor..........................................61
7.1.2.4
25
Ω
Internal Reference Resistor ...........................................61
7.1.2.5
10
Ω
Internal Reference Resistor ...........................................61
7.1.2.6
1
Ω
Internal Reference Resistor .............................................61
7.1.3
Voltage Measurements ..................................................................62
7.1.3.1
Zero Voltage Offsets ..............................................................62
7.1.3.2
Voltage Span Check ...............................................................62
7.2
Adjusting Calibration ........................................................................................................ 63
7.2.1
Calibrate Master Current Source ....................................................64
7.2.2
Calibrating the 400
Ω
Internal Reference Resistor .........................65
