In my microbal fuel cell work, when I am running MFC I measure output by using a multimeter and I am able to measure only current or only Voltage at one time. When I measure both at a onetime the voltage suddenly falls to zero, and the current drops also.
Can any one help me understanding this concept?
How can i solve this problem?
thank you.
I think it is a question how you connect the devices. To me it appears that you short-circuited your cell, which is why the cell voltage dropped to zero. It would be helpful if you could upload a scetch of your circuit.
In my opinion, and from my experience, it is possible to measure current and voltage simultaneously.
On the other hand, R=U/I, or, I=U/R, which means when you know the external ohm ic resistance you can very conveniently translate cell voltage into curretn and vice versa.
Multimeter is designed (Circuit) in such a way that either it applies high resisance to current flow when you measue the potential or it removes the total load and connects the circuit directly ( to give maximum current ) incase if you are measuring current. the earlier one is called open circuit potential and the latter is called short-circuit current.
If you want to measure both then connect a suitable variable resistor in series so that voltage and current remains between the extreme.
I think it is a question how you connect the devices. To me it appears that you short-circuited your cell, which is why the cell voltage dropped to zero. It would be helpful if you could upload a scetch of your circuit.
In my opinion, and from my experience, it is possible to measure current and voltage simultaneously.
On the other hand, R=U/I, or, I=U/R, which means when you know the external ohm ic resistance you can very conveniently translate cell voltage into curretn and vice versa.
To carry out these measurments, you should use a Potentiostat/Galvanostat
No, you don't need a potentiostat/galvanostat. You CAN use one, but to measure, e.g., a power / polarization curve it is not necessary. Here you can use a variable external resistance, over which you measure the cell voltage. Using I=U/R (Ohmic Law) you can calculate the corresponing current flow. Thus, even low-tech equipment would be sufficient for this sort of measurement.
But, In case you want to determine or apply an individual electrode potential (instead of cell voltage) , then you need a potnetiostat.
you can measure both simultaneously.
please check the current modes in the multimeter - AC / DC and range of the current and for voltage
Bhim most multi-meters can measure both voltage and current but normally only one at a time.
Hence if you set the i-meter to measure voltage (and use the voltage inputs - high impedance). this will have to measure the voltage across the cell, hence it is effectively connected in parallel with the cell.
If you set the other to measure current (low impedance) then it must be connected in series with the cell.
-----------------| Cell |------------ (amp meter)----
|--------(voltmeter)---|
Normally the multimeter will have a V (Voltage input), a I (Current input) and a Common.
When you select Voltage mode then connect the probes into V and Common. In this case the probes measure the voltage across the device you are trying to measure
When you select Current mode then you connect probes into I and Common. In this case the probes measure the current flowing through the device you are trying to measure and must be placed in series. It normally has a fuse as well in case the current gets too high.
NEVER SWITCH MODES without first removing probes otherwise big-bang :(
A multiplier is a multipurpose device that can measure both, if you measure one voltage or current other can be calculated with simple ohm formula. Even there are other method for measuring a cell voltage with a bridge condition.
Did youusing the LTC2108 for energy harvesting from a MFC?
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