Flat field feature for the I3200

Lexington, MA (June, 2010) - The I3200 thirty-two channel electrometer is often used to read out a multi-segment detector such as a strip ionization chamber or diode array. The internal calibration function of the I3200 ensures that all the channels are equal in the sense that they all measure current identically. However a typical multi-element detector does not have completely equal sensitivity (expressed as current or charge out per unit input). This is often compensated by the process of "flat-fielding". You apply an equal stimulus to all of the sensors, and derive the factors that give a flat response.

Our customer at the University of Heidelberg requested that this facility be added to the PSI Diagnostic software. It is now available to all customers in version 4.62, which is available on the downloads page (here).

The software stores a compensation offset and gain factor for each channel, which are associated with a particular unit serial number. To measure the offsets, you simply ensure that the stimulus signal is absent, but that a representative background is present, and click the offsets button. Enter the value of the stimulus signal, which can be in any units you like, then apply the uniform flat field stimulus and click the gains button. The factors are calculated and stored.

The compensated values are accessed via a new "Comp" unit selection on the Data screen. In the following example, the first screenshot shows a flat field stimulus measured in absolute current units, in the normal way. The stimulus was used for a compensation calibration, and the second screenshot shows how it then appears when measured in compensated units. The response is flat, as required.

About Pyramid Technical Consultants
Established in 1986, Pyramid serves customers in the USA and Europe from its base in Lexington, Massachusetts and its subsidiary company in England. Pyramid provides instrument control systems for the medical, semiconductor equipment, physics research and biological research markets, providing electronics hardware, embedded real-time software, and host system software drivers and applications.