IEC 1131 Input Types
Original instructions
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Overview
This section describes the voltage and current thresholds for three types of input, as defined by IEC 1131.
Thresholds
The following table shows the voltage and current thresholds for three input types at 24 VDC, as defined by IEC 1131.
Input Type
On Voltage
On Current
Off Voltage
Off Current
Type 1
+15 ... +30 V
2 ... 15 mA
-3 ... +5 V
... 15 mA
Type 1+
+11 ... +30 V
2.5 ... 10 mA
-3 ... +5 V
... 10 mA
Type 2
+11 ... +30 V
6 ... 30 mA
-3 ... +5 V
... 30 mA
Type 1+
This type is often used for active sensors and relays because the minimum on and maximum off current thresholds are higher.