Discriminator

[ASU]

Are disciminators part of a NI  DAQs internal functions?

I'm testing a photomultiplier (PMT) and a discriminator circuit is a fundamental part of the data acquisition system.

[mallorim]

Hi ASU,

When you mention discriminators, are you talking about a softawre filter, or are you asking if a discriminator circuit is a part of the actual DAQ hardware?

Regards, Mallori M.

[ASU]

What I mean is this,  Once the PMT detects a light source it outputs a negative current pulse which we want to amplify thru an wideband (1.6GHz) op amp. When it reaches this stage there are unwanted noise pulses that need to be filtered. The typical way is to build a discriminator (comparator) circuit which in its own self is also called a threshold detector, to pass certain pulses and reject others then output this as an TTL signal to a counter which we do know a DAQ can analyze so as to plot a fluorescence decayed histogram . We are talking about low ns pulses. So instead of building this circuit we wanted to know if a DAQ has this capability.

[mallorim]

Hi ASU,

Is sounds like what you are interested in is analog level triggering. Depending on the DAQ card you purchase and use since not all DAQ cards have this capability, you can define a voltage level above which you trigger data acquisition. Everything below that voltage level is not recorded. The Developer Zone article Analog Trigger discusses what is entailed in analog triggering and how it works. The Knowledge Base What is the Minimum Signal Width for an Analog Trigger on an NI Data Acquisition Board? discusses the minimum width of a pulse that can trigger the analog reading. 

Hope this explanation helps. 

Mallori M.