Omega OM-USB-1208FS manual External trigger, External clock input/output, Counter

OM-USB-1208FS User's GuideSpecifications

External trigger

Table 12. Digital trigger specifications

Parameter	Conditions	Specification
Trigger source (Note 6)	External Digital	TRIG_IN
Trigger mode	Software selectable	Edge sensitive: user configurable for CMOS compatible
		rising or falling edge.
Trigger latency		10 µs max
Trigger pulse width		1 µs min
Input high voltage		4.0	V min, 5.5 V absolute max
Input low voltage		1.0	V max, –0.5 V absolute min
Input leakage current		±1.0 µA

Note 6: TRIG_IN is a Schmitt trigger input protected with a 1.5 kilohm (kΩ) series resistor.

External clock input/output

Table 13. External clock I/O specifications

Parameter	Conditions	Specification
Pin name		SYNC
Pin type		Bidirectional
Software selectable direction	Output (default)	Outputs internal A/D pacer clock.
	Input	Receives A/D pacer clock from external source.
Input clock rate		50 KHz, maximum
Clock pulse width	Input mode	1 µs min
	Output mode	5 µs min
Input leakage current	Input mode	±1.0 µA
Input high voltage		4.0	V min, 5.5 V absolute max
Input low voltage		1.0	V max, –0.5 V absolute min
Output high voltage (Note 7)	IOH = -2.5 mA	3.3	V min
	No load	3.8	V min
Output low voltage (Note 7)	IOL = 2.5 mA	1.1	V max
	No load	0.6 V max
Note 7: SYNC is a Schmitt trigger input and is over-current protected with a 200 Ω series resistor.

Counter

	Table 14. Counter specifications
Pin name (Note 8)	CTR
Counter type	Event counter
Number of channels	1
Input type	TTL, rising edge triggered
Input source	CTR screw terminal
Resolution	32 bits
Schmidt trigger hysteresis	20 mV to 100 mV
Input leakage current	±1 µA
Maximum input frequency	1 MHz
High pulse width	500 ns min
Low pulse width	500 ns min
Input high voltage	4.0 V min, 5.5 V absolute max

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