Basic function principles
Properties
The KL320x analog input terminals enable resistance sensors to be connected directly. A micro-controller within the terminal is used for converting and linearizing the resistance to a temperature value. The temperatures are displayed as follows:
- for KL3201, KL3202, KL3204, KL3204-0030:
- Measuring range 10 to 5000 Ω: 1/2 °C (1 digit = 0.5 °C)
- Measuring range 10 to 1200 Ω: 1/10 °C (1 digit = 0.1 °C)
- All other measuring ranges: 1/10 °C (1 digit = 0.1 °C)
- for KL3204-0030:
- Measuring range -40°C to 110°C: 1/10 °C (1 digit = 0.1 °C)
- Resistor at 0°C: 27 280 Ω
Note: since there are different NTC10K types, this value characterizes the characteristic curve stored in the KL3204-0030.
In addition to this, a broken wire or short circuit is reported to the Bus Coupler or to the controller, and indicated by the ERROR LED.
PT100, NI100, PT200, PT500, NI120, NI1000 and PT1000 as well as NTC10K of the KL3204-0030 elements are implemented over their full measuring ranges as resistance sensors. The terminal can be fully configured over a fieldbus. A self-defined scaling of the output can, for instance, be performed, or the temperature conversion can be switched off. In the latter case, the measurement is output in the range from 10 Ω up to 1.2 kΩ with a resolution of 1/16 Ω (the internal resolution of the resistance value is 1/255 Ω).
Process data output format
In the delivery state, the measured value is displayed in increments of 1/10° C in two's complement format (integer). The complete measuring range is output for each resistance sensor. Other display types can be selected via the feature register (e.g. sign/amount representation, Siemens output format).
|
Measured value |
Hexadecimal output |
Signed integer output |
|---|---|---|
|
-250.0°C |
0xF63C |
-2500 |
|
-200.0°C |
0xF830 |
-2000 |
|
-100.0°C |
0xFC18 |
-1000 |
|
-0.1°C |
0xFFFF |
-1 |
|
0.0°C |
0x0000 |
0 |
|
0.1°C |
0x0001 |
1 |
|
100.0°C |
0x03E8 |
1000 |
|
200.0°C |
0x07D0 |
2000 |
|
500.0°C |
0x1388 |
5000 |
|
850.0°C |
0x2134 |
8500 |
Resistance limit values
- R > 400 Ω: Bits 1 and 6 (over range and error bits) in the status byte are set.
The linearization of the characteristic curve is continued with the coefficients of the upper range limit up to the limit stop of the A/D converter (approx. 500 Ω for PT100).
- R<18 Ω: Bits 0 and 6 (under range and error bits) in the status byte are set.
The smallest negative number is displayed (0x8001 corresponds to -32767).
For over range or under range the red error LED is switched on.
Process data
The process data that are transferred to the terminal bus are calculated using the following equations:
|
Variable |
Meaning |
|---|---|
|
X_RL |
ADC value of the supply cables |
|
X_RTD |
ADC value of the temperature sensor, including one supply cable |
|
X_R |
ADC value of the temperature sensor |
|
A_a, B_a |
Manufacturer gain and offset calibration (R17, R18) |
|
A_h, B_h |
Manufacturer scaling |
|
A_w, B_w: |
User scaling |
|
Y_R |
Temperature sensor resistance value |
|
Y_T |
measured temperature in 1/16 °C |
|
Y_THS |
Temperature after manufacturer scaling (1/10 °C) |
|
Y_TAS |
Temperature after user scaling |
|
Y_AUS |
Process data to PLC |
a) Calculation of the resistance value:
X_R = X_RTD-X_RL (1.0)
Y_R = A_a * (X_R - B_a) (1.1)
b) Curve linearization:
Y_T = a1 * Y_R2 + b1* Y_R + c1 (1.2)
or
Y_T = Y_R if output in Ω (1.3)
c) Neither user nor manufacturer scaling are active:
Y_AUS = Y_T (1.4)
d) Manufacturer scaling active (factory setting):
Y_THS = A_h * Y_T + B_h (1.5)
Y_AUS = Y_THS
e) User scaling active:
Y_TAS = A_w * Y_T + B_w (1.6)
Y_AUS = Y_TAS
f) Manufacturer and user scaling active: (1.7)
Y_1 = A_h * Y_T + B_h
Y_2 = A_w * Y_1 + B_w
Y_AUS = Y_2
