Daedalon EC-33 Gebrauchsanweisung - Seite 4

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EC-33 Geiger Computer Interface USB

number is so high that it would cause pileup and damage the Geiger tube (as

well as the experimenter!)

An 8 bit analog to digital converter measures voltage. One measurement is

taken every 20 ms and included in the packet that contains counts. Host

software displays a number taken by averaging 50 measurements, thus yielding

a higher effective resolution.

Dead time for a Geiger Counter is defined as a period of time for which the

counter will miss counts during each measurement interval. Dead time for the

counter is less than 2 microseconds, although if a pulse transition occurs

during this brief interval, it is still captured by the microcontroller. Pulse widths

coming from the Geiger tube are much longer than 2 microseconds, thus

effective dead time is zero.

Communication on the USB is very robust. The electrical design of the interface

is very conservative, using differential signaling. In addition, handshaking and

CRC error checking are built into the protocol. If data were to be corrupted

during transmission, the packet will be sent again to the host.

If the host computer goes into suspend mode (sometimes called standby or sleep

mode), the EC-33 will go into a very low power mode where it draws less than

500 µA. When the computer is reactivated, the Interface wakes up, and is ready

for use.

Troubleshooting

If the Interface "STATUS" light is not yellow after plugging it in, here are some

tips to try and uncover the problem.

Be sure that the computer is running Windows 98, or

Windows 2000, or newer. USB support in Windows

95 is not complete, and there is no USB support in

Windows NT.

If the Interface is connected to a hub, be sure it is a

self-powered hub, and that the power cable is

plugged into it properly. Most hubs will operate as

self-powered or bus powered depending on whether

the A/C adaptor is connected. Devices that appear

to be USB "splitters" are, in fact, bus powered hubs,

and the Geiger Interface will not work with them.

Determine whether other USB peripherals will work

on the current machine. A mouse or keyboard may

be borrowed from another machine and connected

for testing. USB keyboards and mice are inter-

changeable across platforms, so a Macintosh USB

mouse may be used on a PC and vice-versa.

If another known-good peripheral does not work on

this computer, it may be necessary to use the

Windows Device Manager to find out why. Look for a

device category called "Universal Serial Bus