Key Digital ES381 manual Performance, Miscelaneous

Isolation rating:	300V CAT II, 500V CAT I between BNC
Transient isolation17:	ground and USB ground
	BNC ground to USB ground +/-2.5KV

4.4.2 Performance

Measurement modes:	Frequency and Period
RUN mode:	Continuous readings
STOP mode:	Readings frozen
ONCE mode:	Single reading returning to STOP
Input connector:	BNC
Input DC resistance:	1Meg to GND for inputs between (GND-0.4V)
	and (INPUT SUPPLY + 0.4V). Outside these
	ranges DC resistance approximately 90KOhms
Input capacitance:	20pF typical
Input 3dB bandwidth:	100MHz typical
Input protection:	±30V max to GND
Input supply:	1.50V to 5.00V in 256 steps of 13.7mV to suit
	external logic environments (see 2.2)
Main counter:	28-Bits with overflow detect bit
Maximum count rate:	Guaranteed 50MHz, typically 100MHz with
	input signal suitable to trigger input threshold
Master clock:	12.50MHz, initial accuracy ±0.01%, ageing and
	drift after 1 year ±0.005%, temp coefficient
	±0.005% /oC
Master clock skew:	For 2 or more stacked USBcount50s, typical 2ns
	between units
Internal reference clocks:	100MHz, 10MHz, 1MHz from internal PLL
	clocked by master clock
Internal reference periods:	0.1s, 1s, 10s divided from master clock
Period edge detection:	FALLING->FALLING, RISING->FALLING,
	FALLING->RISING, RISING->RISING

4.4.3 Miscelaneous

USB transfer rate:	USB 1.118 Full Speed 12MBits/sec
USB device ID:	10C4 F004

17This figure derives from the 300V CAT II isolation rating and defines the peak transient voltage that can be safely tolerated between the BNC ground and the USB ground.

18Works in USB 1.1 or USB 2.0 hosts using the 12MBits/sec full speed mode

Elan Digital Systems Ltd. 29 USBcount50 USER’S GUIDE Iss1