The SEII card in your computer interfaces to your pulse processor and transmits data which allows your EDS application (DTSA or FLAME) to acquire and display an X-ray spectrum. Pulse processors create a rather simple output signal that can be simulated with a pulse generator. This lends itself to a particularly simple way to diagnose the basic operation of the board. The concept is to simulate the acquisition of an X-ray spectrum with a pulse generator. With this simulation, you can prove that the SEII X-ray acquisition functions are performing correctly (or not).

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Step 1:

You must procure a pulse or waveform generator. The output pulses should ideally be about 2.5 microseconds in width, with a baseline of zero volts and a peak amplitude on the order of 1-5 volts. The width can be larger than 2.5 microseconds, but the results may not agree precisely with what we show on this page (it will be pointed out where discrepancies might occur). Disconnect the ribbon cable from the back of the SEII card in the computer and set the ribbon cable aside. Then, using your favorite connection scheme (we suggest paper clips), wire the SEII card rear connector as follows:

What you're doing: The pulse generator creates a fake x-ray pulse which can be injected into the PHA analog input. The SEII generates a pulsing TTL ADC-busy signal on pin 4 in response. This line is asserted for 8 microseconds in the version 2.1 hardware, and for 6.7 microseconds in the 2.2 hardware. Via the above connections, this ADC-busy signal is used to send a simulated fast channel input to pin 2 and a simulated Live Time signal to pin 3.

Step 2:

Launch DTSA and open the Hardware Setup dialog box via the DTSA Acquire menu. Make sure the dialog items are configured exactly as shown below. Set the pulse processor to custom, and make sure all polarities are set to low. If the option to select step or no-step is visible, select step (this option is not visible on the v2.2 card).

When the dialog is set up correctly, hit OK to return to the DTSA spectrum display window (blue).

Step 3:

From the Acquire menu again, select Clear/Start. The DTSA meters should now display something similar to this: 

Real-time and livetime counting together but not necessarily equal

Deadtime about 1%

Input = Output (actual value should equal frequency of pulse generator)

Under these circumstances, the DTSA spectrum window should show a narrow peak as shown below:

Note: the actual energy-position of the peak will depend on the amplitude of the test pulse. A 10-Volt pulse is full-scale and will be binned to channel 4095. At 10 eV/channel this is about 41 keV. The recommended 1-5 volt pulse will appear between channels 410 and 2048 (4 keV and 20 keV for 10 eV/channel). In DTSA, be sure to select the number of channels shown to 2K, and set Auto Scale to on. In addition, depending on the quality of the pulse generator, the observed peak may not be as narrow as the one shown.

Step 4: Additional Check of Pulse Reject Circuitry

Open the Hardware Setup dialog box via the DTSA Acquire menu again. Set the Pulse Reject polarity to high as shown below and hit OK. Upon return to the DTSA spectrum display window, the meters should display zero output counts:

Final Analysis: If you see the behaviors described above, there is nothing wrong with the basic EDS operation of the SEII card. You must look elsewhere for your problems.