I am in need of a DAQ device that can generate both positive and negative constant current. I will be using it to charge/discharge a capacitor repetitively. The DAQ 9265 seems to provide only positive constant current from 0 to 20 mA. So I can charge my capacitor with it but I cant discharge with it. Is there a DAQ device in the market that can solve my purpose?
The 20mA signal is because that is a standard signal for sensors in industrial settings.
For arbitrary current sources, you might want to look at a Source Mearsurement Unit (SMU).
If you apply the capacitor , why not a voltage controlled current source?
I like this idea:
or for very small currents
You are right. I can do with a voltage source like NI-USB 6351. That would produce a time varying current.
But in the literature, they generally charge/discharge supercapacitors at constant current.
So I was wondering if there was any instrument available which can generate, say +10 mA for a custom amount of time and -10 mA for another custom amount of time. There can also be some rest period in between the two.
IF you tell us what your basic goal is we migth find a simple solution 🙂
A simple curent limiter (say a resistor or more fancy a two pole current 'source' in a diode bridge to make it bipolar) migth be all it needs.
But such circuits have a burden voltage ... so, as more specs you tell, as better we can help 😄
As Henrik says, the first step is to specify what you want to do. If you are doing capacitor charge/discharge experiments then you need to look into the voltage that the constant current instrument is able to supply.
So the voltage across your capacitor will increase as you charge it. As you mention the term "Super Capacitor" I assume that you want to store a large charge. So you need to check that the voltage capability of your constant current instrument meets your requirements as well as the current capability.