FAQ about Measurement Technique

What is the difference between the current scan lin, the current scan high res and the current scan shunt?

What is the resolution in size, respectivly how large are the measurement cells?

What is the maximal size of a sensor plate respectively measurement device?

What is the maximal working temperature of the device?

How thick are the sensor plates?

Can we have milled channels into the surface of the sensor plate so that we can use it as a flow field?

My design has many bolts or many respectively large manifolds. Is it possible to build a sensor plate with openings for bolts and fluids?

Can we have channels for sealing in the sensor plate?

What is the maximal compression force which can be applied to a sensor plate?

We have no place to connect the electronic of the current scan lin to the sensor plate. Can we connect the electronic with cables?

Is the sensor plate compatible with our media?

Some of the contact segments show corrosion! Is this harmful?

Answers:

What is the difference between the current scan lin, the current scan high res and the current scan shunt?

There are two main differnces. The first is the complexity. In the current scan high res for each contact segment respectively measuremnet cell one wire is necessary. So for an array with n x n segments n² wires are necessary. The complexity of the current scan shunt is also quadratically but here is even a pair of wires necessary for each measurement cell. With the current scan lin the complexity is linear. This means, for an array with n x n segents only 2n pairs of wires are necessary. So the current scan high res as well as the current scan shunt are restricted to small cells or have a lower resolution whereby the current scan lin can also be applied for very large cells with a constant resolution.
The other difference is that the current scan high res is a multiple electronic load for the single cell fuel cell. Whereby the measurement with the current scan lin or current scan shunt do not influence the operation of the fuel cell. So the current scan lin as well as the current scan shunt can be used in fuel cell stacks.


What is the resolution in size, respectivly how large are the measurement cells?

The measurement cells of the current scan lin are approximately 7mm x 7mm. Approximately means that the measurement cells can be stretched a little bit to cover the whowl active area. But they can not be made smaller because of the two toroid ferrite cores which are placed inside each measurement cell. If the measurement cells would be made larger the maximal current per cm² would sink.
The size of the contact segments of the current scan high res depends on the setup of the sensor plate. The range is from 1mm x 1mm to 2mm x 2mm. If the segments are made smaller it is not possible to contact the segments with a conductor path. Of course the segments can be made larger, but the current per segment is limited to 20mA. So the current per cm² may sink to an unusable value.
For the current scan shunt the resolution depends mainly on the ability to lead through the conductor paths. Also measurement range can be varied over a wide range because the shunt resistor can be adapted.


What is the maximal size of a sensor plate respectively measurement device?

The size for a current scan high res is restricted by the quadratic complexity and the power output of the amplifiers. The maximal size is in the range from 25cm² to 50cm². The size for a current scan lin and current scan shunt is restricted by the ability to manufacture a printed circuit board. The sensor plate may have a maximal size of 500mm x 360mm.


What is the maximal working temperature of the device?

The working temperature for the electronic is 0-40C. (Ambient conditions, humidity non condensing.) For the sensor plates there are two different materials available. The on is the well known FR4. The working temperature for this is up to 100C. The other material is a polyimide base material. The working temperature for this is up to 180C.


How thick are the sensor plates?

The sensor plates for the current scan lin are approximately 3.5mm.
The sensor plates for the current scan high res are approximately 2mm.
The sensor plates for the current scan shunt can vary over a wide range. The least thickness is approximately 0.5mm.


Can we have milled channels into the surface of the sensor plate so that we can use it as a flow field?

For the current scan lin this is not possible because there are conductor paths approximately 0.2mm under the surface. The sensor plates can not be made thicker because of problems during manufacturing.
For the current scan high res it is within some restrictions possible.
The sensor plates for the current scan shunt can be designed in a away that nearly arbitrary channels can be milled into the surface. So the sensor plate can be used as a flow field.


My design has many bolts or many respectively large manifolds. Is it possible to build a sensor plate with openings for bolts and fluids?

The sensor plate for the current scan lin can have nearly arbitrary many openings. There must be only enough space for the conducting paths going in and coming out of the measurement cells.
The sensor plates for the current scan shunt also may have nearly arbitrary many openings. But this will reduce the resolution because there is less space for the conductor paths.
The sensor plates for the current scan high res may have only openings on two oposite sides of the active area. The other two sides are nearly completely reserved for the conducting paths.


Can we have channels for sealing in the sensor plate?

For the current scan lin normally approximately 0.2mm under the surface of the sensor plate there are conducting paths. So the channels are restricted. But a special design can be used enabling nearly arbitray channels from one side.
For the current scan high res the depth of the channels is restricted because of the conducting paths.
The sensor plates for the current scan high res may have only openings on two oposite sides of the active area. The other two sides are nearly completely reserved for the conducting paths.


What is the maximal compression force which can be applied to a sensor plate?

The sensor plates are very robust. Normaly you will destroy MEA, GDL and bipolar plates made out of graphite befor a sensor plate is damaged. But of course high point forces, for example in an area with a sealing, may damage the sensor plate.


We have no place to connect the electronic of the current scan lin to the sensor plate. Can we connect the electronic with cables?

It is recommended to connect the electronic directly to sensor plate. This has two reasons. At first current signals have to be feed into the sensor plate and the cables will lead to a high voltage drop. Then the signals delivered by the measurement cells are very low and a cable would lower the signal quality.
But special cable solutions are available on request.


Is the sensor plate compatible with our media?

The contact segments should be sealed so that no media can contact them. Otherwise this can lead to corrosion because the gold plating is no hermetically sealing. There may be impurities or even scratches. The rest of the material is compatible with water, deionised water and methanol solution. If you use special cooling liquids or other media the compatibility should be tested befor you order a device. A special sealing may be necessary.


Some of the contact segments show corrosion! Is this harmful?

Yes, it is. It should be repaired immediately. You can do it with a tampon galvanisation.