Multi channel detector continuity tests

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The multi channel detector (MCD) assembly found on Physical Electronics 5500 through 5800 X-ray photoelectron spectroscopy (XPS) systems comprises two pieces – the channel plate assembly and the connection flange.

If you follow the procedure in the 10-360 spherical capacitive analyzer manual you can replace the channel plates (Chevron type) without too much difficulty. Two things to remember are to use some small Allen wrenches to hold the pins up (that removes the spring tension) and to make sure that the little marks on the channel plates face each other.  This drawing might be helpful – MCD detail

But equally important as installing the channel plates correctly is ensuring that you have good continuity on all of the pins on the connection flange, and that you are making a good electrical contact with the channel plate assembly when you install the flange.

Before you install the connection flange, short out the pins on the connector flange with aluminum foil as shown in the pictures below. Then use an ohmmeter to measure the continuity of each pin to the flange. Each pin should have a resistance of less than 2 ohms. Sometimes the pins can become oxidized and if so the resistance can be high, as high as Meg ohms. If the resistance on one or more pins is high, very carefully use a tweezers and pull up on the wire on the end that is close to the connector. Move it no more than 1/16″ up and down. If you move it up too high, the pin will come off the connector pin and it is very difficult to put those back on. Verify that each pin has good continuity and is all the way down before installing the connection flange.

When you install the connection flange (after first installing the channel plate assembly inside the SCA) measure the capacitance of each pin to the chamber. They should all have the same capacitance, typically about 250 pf. The 4 middle pins are not used so their capacitance will be about 100 pf. If the other 16 pins do not all have the same capacitance, then the some of the spring contacts are not making contact with the channel plate assembly. Try rotating the flange a little bit. You may need to slide the connection flange back a little bit and then reseat it. Just be sure that each pin has the correct capacitance before tightening the connection flange.

Finally, the pins on the connection flange may have been bent slightly during the continuity test. Visually inspect the pins and carefully slide on the MCD preamp to make sure that it will go on without bending any of the pins. Adjust the pins as needed until the MCD preamp can go on easily. The pins on the connection flange are very soft and can bend easily. It is possible to force the MCD preamp down on a bent pin and if so, the pin will usually break when you try to straighten it. So just be aware that this and you will not bend the MCD pins.

RBD Instruments provides the MCD channel plates and technical support to help you with the installation.

 

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