Basic Function Principles - Beckhoff KL320 Series Documentation

Product overview
2.3

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
-250.0°C 0xF63C
-200.0°C 0xF830
-100.0°C 0xFC18
-0.1°C 0xFFFF
0.0°C 0x0000
0.1°C 0x0001
100.0°C 0x03E8
200.0°C 0x07D0
500.0°C 0x1388
850.0°C 0x2134
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.
16
Signed integer output
-2500
-2000
-1000
-1
0
1
1000
2000
5000
8500
Version: 4.4 KL320x