write to a relay

[smm]

I am writing to a relay using Port 0 line 0. When this relay is powered up, it gets depressed and is released really quickly. I'm reading off another contacter from Port 1 line 0. I want to be able to perfom a read within the period the relay gets suppressed and is released.

This perios is less than 1 sec. How do I perform a write to a relay, and consequently read from a contacter within a period of less than 1 sec

[smm]

I want to check for bouncing of the relay- contacter. I know for a fact that an oscilloscope can test it bt I'm not sure why I cannot do this using a DAQ. I'm using Labview 8.5 with the NI-USB 6501

[smercurio_fc]

What is it that you're trying to find out? The bounce time? This should be a spec for the relay. Most relays bounce more than once, so which bounce are you trying to catch? More than likely you're just sampling at a point in time when the relay is contacted. You really need to configure the DAQ card to read a set of points, just like the scope does. It's unlikely that you will be able to catch it by simply reading once. Even if you did catch it, it wouldn't be reliable.


Message Edited by smercurio_fc on 01-10-2008 08:44 AM

[smm]

Can you tell me, how can I find out the period between each read for the DAQ unit? Like can I count the time period for a continuos read.

[johnsold]

I am not familiar with your particular DAQ device, but you should be able to do a hardware timed acquisition. The the time between samples is the reciprocal of the sampling rate. If the output is an array just determine the index of the start of the transition and the index of the last bounce, subtract and multiply by the time between samples. If the output is a waveform datatype, the time between samples is the dt value available via the Get Waveform Components function.

Set the sampling rate at 1000 to 10000 samples per second, depending on the type of relay or contactor and what timing resolution you want.

Lynn

[smercurio_fc]

The USB 6501 is just a simple digital I/O module, software timed. It does have a counter, so you can probably use that, but I'm not entirely sure, given the kind of DAQ module that it is.