Pulse measurement specifications

The data logger can measure switch closure or high-frequency pulse signals on C and U terminals. Terminals are configured as pairs with options for pull-up or pull-down. Even-numbered U terminals can be configured as low-level AC inputs. See also Digital input/output specifications. Each terminal has its own independent 24-bit counter. Terminal pairs are U1 and U2, U3 and U4, through U11 and U12.

NOTE:

Conflicts can occur when a control port pair is used for different instructions (TimerInput(), PulseCount(), SDI12Recorder(), WaitDigTrig()). For example, if C1 is used for SDI12Recorder(), C2 cannot be used for TimerInput(), PulseCount(), or WaitDigTrig().

Pulse Event: Transition from logic low to logic high.

Terminal Pair Configuration	Logic Low	Logic High
5 V	≤ 1.5 V	≥ 3.5 V
3.3 V	≤ 0.8 V	≥ 2.0 V

Sustained Input Voltage without Damage: ±20 VDC

Maximum Counts Per Scan: 2²⁴

Input Resistance: 5 kΩ

Accuracy: ±(0.02% of reading + 1/scan)

Low-level AC input

Terminals: U2, U4, U6, U8, U10, U12

NOTE:

When an even numbered U terminal (for example, U2) is used for low-level AC pulse counting, its paired odd numbered terminal (U1 in this example) can be used only for switch-closure.

DC-offset rejection: Internal AC coupling eliminates DC-offset voltages up to ±0.05 VDC

Input Hysteresis: 12 mV at 1 Hz

Low-Level AC Pulse Input Ranges for U Terminals :

Sine wave (mV RMS)	Range (Hz)
20	1.0 to 20
200	0.5 to 200
2000	0.3 to 10,000
5000	0.3 to 20,000

Switch closure input

Terminals: C1-C4, U1-U12

Resistance: Configurable in terminal pairs with 100 kΩ pull-up or pull-down

Maximum Input Frequency: 150 Hz

Minimum Switch Closed Time: 5 ms

Minimum Switch Open Time: 6 ms

Maximum Bounce Time: 1 ms open without being counted

Software Debounce Time: 3.3 ms

High-frequency input

Terminals: C1-C4, U1-U12

Resistance: Configurable in terminal pairs with 100 kΩ pull-up or pull-down

Typical Wave Form: 5 or 3.3 VDC square wave

Maximum Input Frequency: 1 MHz