Voltage reference
Voltage reference
(OP)
I am building a device for corrosion testing. To do corrosion testing, the part being tested is submerged in an electrolyte and a current is passed through it. The voltage source is controlled and the current is measured. These are plotted against one another and at a certain voltage, a breakdown of the part can be seen (corrosion).
The device consists of a precision power supply capable of outputting a voltage from -0.6V to about 0.8V and then back to -0.6V. The voltage is increased at a rate of 1mV / second and needs to be accurate to within 1mV. The current is measured using a picoammeter and the current ranges from tenths of microamps all the way up to about 10 milliamps. The current measurement problem can be solved by purchasing a picoammeter which I have done. However, the voltage source may pose an issue. I haven't been able to find voltage source that is both programmable, low-noise (0.5mV or less), and capable of positive and negative voltages.
The closest thing I have found is a power supply (BK Precision 9150) that can output from 0V - 5V and is very precisely controlled (0.1mV line regulation , 0.5mV load regulation)as well as programmable. The problem is that it does not output negative voltages which I need. Is there a way to add in a negative voltage to the output of this power supply to bring the voltage down to -0.6V?
I am thinking about using an op amp to level shift the voltage into the negative region, but the output from the op-amp will be as noisy as it's rail voltages right? I am worried that the op-amp stage will potentially ruin my clean signal coming from my power supply.
Any ideas would be greatly appreciated.
Thanks
The device consists of a precision power supply capable of outputting a voltage from -0.6V to about 0.8V and then back to -0.6V. The voltage is increased at a rate of 1mV / second and needs to be accurate to within 1mV. The current is measured using a picoammeter and the current ranges from tenths of microamps all the way up to about 10 milliamps. The current measurement problem can be solved by purchasing a picoammeter which I have done. However, the voltage source may pose an issue. I haven't been able to find voltage source that is both programmable, low-noise (0.5mV or less), and capable of positive and negative voltages.
The closest thing I have found is a power supply (BK Precision 9150) that can output from 0V - 5V and is very precisely controlled (0.1mV line regulation , 0.5mV load regulation)as well as programmable. The problem is that it does not output negative voltages which I need. Is there a way to add in a negative voltage to the output of this power supply to bring the voltage down to -0.6V?
I am thinking about using an op amp to level shift the voltage into the negative region, but the output from the op-amp will be as noisy as it's rail voltages right? I am worried that the op-amp stage will potentially ruin my clean signal coming from my power supply.
Any ideas would be greatly appreciated.
Thanks





RE: Voltage reference
I may be missing something, though -- let some of the others pitch in too.
Good on ya,
Goober Dave
RE: Voltage reference
I don't have a ton of experience in analog electronics, so I can't be sure this is possible, but I'm thinking if I found a low noise, adjustable negative voltage source, then I could add it into the BK9150 output voltage to make my negative voltage. However, finding something with the precision I need has been tough.
RE: Voltage reference
It's the closest I could come with my Google kung fu...
If none of the regular contributors in this forum (of whom I stay in awe) come through for you, you might try re-posting in the measurement and control instrumentation engineering forum...
Good on ya,
Goober Dave
RE: Voltage reference
htt
On its 2V range, its programming resolution is 50 uV, and measures down to 10 pA resolution.
Yokogawa, which used to be the manufacturer of the HP4145 semiconductor parameteric analyzer might also be a possible source of similar equipment.
TTFN
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RE: Voltage reference
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RE: Voltage reference
RE: Voltage reference
RE: Voltage reference
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RE: Voltage reference
An opamp should do it easily.
How about a bipolar digital to analog converter with a precision voltage reference, and enough bits to give microvolt resolution.
RE: Voltage reference
@Warpspeed: I tried doing exactly that, but ran into problems with noise. With the resources at hand, I managed to minimize the noise to 20mV, but need more like 0.5mV.
RE: Voltage reference
A suitable L/C low pass filter should be able to attenuate that to well within your requirements.
Anyhow, glad to hear you have now found a solution.
RE: Voltage reference
If you had a ±50 Volt supply with a 10:1 Voltage divider that might work. I haven't thought it through, the idea just jumped out.
RE: Voltage reference