Daedalon EC-33 Buku Petunjuk - Halaman 3

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EC-33 Geiger Computer Interface USB

Place the Windows distribution CD in the CD-ROM drive, and select CD-ROM

drive when the following dialog appears. If the Windows distribution CD is not

available, it is possible that the driver is in the default location suggested by the

"Specify Location" selection:

Click Next when the following dialog appears:

If all is well, Windows reports back with the following dialog box. If the

"STATUS" light is still red, try disconnecting, then reconnecting the interface. If

the LED does not turn yellow within a few seconds, see Troubleshooting.

With Windows 98/ME, this procedure may need to

be repeated for every USB port on the computer. It

would be worthwhile repeating step 5 for each port

now.

The "COUNTS" LED should flash whenever the GM

tube detects an ionizing particle. If the rear panel

switch is on, there will be a short audible beep for

every detected event as well. This verifies operation

of the tube and Interface.

Installation of the EC-33 Geiger Computer Interface is now complete. See the

software manual, (Windows or Macintosh), for details on software installation

and operation.

Hardware Description

The EC-33 connects to a computer via its USB port. It is a low speed device,

compliant with Version 1.1 of the USB specification. It will operate with any

USB port that meets version 1.0 or newer of the USB specification as defined by

the USB Implementers Forum. Power is drawn directly from the USB port, with

a maximum of 250 mA.

The Interface contains a regulated switching power supply to generate the high

voltage required for Geiger-Müeller tubes. Two fixed voltage presets provide

outputs of 500 Vdc and 900 Vdc, adequate for most GM tubes. A third setting

allows continuous adjustment of voltage from 0-1200 Vdc via a front panel

control.

Counts generated by the Geiger tube are generally on the order of tens of

microseconds. The pulse widths are stretched to 20 ms, so that the counts LED

is visible to the human eye. This stretched pulse controls the audible

transducer as well.

Counts from the tube are collected by the on-board microcontroller during 20

ms intervals, then sent back to the computer. The microcontroller clock is

synchronized with the USB timing, which in turn is controlled by a crystal inside

the host computer.

An 8-bit integer received by the computer represents the counts collected during

the measurement interval. Note that the limit for an 8 bit integer is 255. This

limit is more than sufficient, as the counting rate required to exceed this