PCI-7390 MCA-7790Y General purpose input from BNC signal generator (voltage range)

[splider]

Hi, 

I am using PCI-7390 and MCA-7790Y to control motors. I want to send a signal to General Purpose Input through Pin #7 on MCA-7790. From the specifications, there are two limits for both voltage and current. I am wondering, since I make the external input voltage in the working range, if I still need to worry about whether the input current will excess the maximum Turn-on current. 

Now the external signal is coming from a BNC box (Berkeley Nucleonics Corporation, Model 500A Digital Delay Generator). The output of its signals are:

OUTPUTS

(T1,T2,T3,T4)

1. IMPEDANCE 50 W

2. SLEW RATE > .2 V/ns

3. OVERSHOOT < 100 mV + 10% of pulse amplitude

4. AMPLITUDE 1-10V into 50W load 2-20V into high impedance load manually adjusted,

all outputs at same level.

1. PEAK CURRENT 400 mA per channel

2. AVERAGE CURRENT 200 mA average (total for all channels) 

Thanks in advance.

Qi 

[Buechsenschuetz]

I am not familiar with these devices but it seems that your systems wants TTL level signal at its inputs. TTL voltage level for logic HIGH state is 2.8V minimum and 5.0V maximum, so the output of your pulse generator should be set to a proper level. A TTL input is high impedance (from an analog point of view). Set the output level to minimum, connect the generator to your system and check output pulse height with an oscilloscope. Since output impedance of the generator is low (50 ohms) it will fulfill the requirement of a low impedance in logic LOW state for TTL level signals.

For a very proper solution you should use two gates of a Schmitt trigger device such as an 74LS14 which will translate the output signals of your generator to very proper TTL signals. But I think the system will work without this.