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SC-TDC-1000 S Series Manual
SC-TDC-1000 S Series Manual | Surface Concept GmbH
4.2.1 TDC Stop Inputs
The SC-TDC-1000 S devices come with 8 (R012, R013) or 16 (R022, R042) stop input channels. All stop
signals must be applied as LVTTL (minimum amplitude of at least +2.1V on 50Ohms) signals to the “STOP
INPUTS” (BNC socket). There is an exception for the R042, where all stop signals must be applied as NIM
signals to the “STOP INPUTS” (LEMO 00 socket).
4.2.2 TDC Start Input
An external start signal must be provided to the TDC for real time resolved measurements. The external start
signal must be applied as a LVTTL (minimum amplitude of at least +2.1V on 50Ohms) signal to the “START
INPUT” (BNC socket) for R012, R013 and R022 and as NIM signal to the “Start Input” (LEMO 00 socket) for
R042. In addition the software must be set to accept external start signals, by changing the corresponding
entry in the tdc_gpx3.ini file.
The corresponding entry in the tdc_gpx3.ini file is:
Ext_Gpx_Start = X
X is either NO or YES.
The default setting is YES
.
“Ext_Gpx_Start” = YES must be set for the TDC to accept the external start signal.
In addition the following entries in the tdc_gpx3.ini must be set as follows:
StartCounter = YES
StartPeriod = 0x800000
Measurements are performed in respect to an internal start signal of the TDC when “Ext_Gpx_Start” =
NO. This internal start signal has no time correlation to any external clock and therefore also not to the
incoming stops. Any external start signal must be disconnected from the start input of the TDC, when
working with the internal start signal.
The rise time of the start signal is of great importance, the faster the rise time, the better the time resolution.
The maximum frequency of the start pulse must not exceed 7MHz.
Note
Do not forget to save the ini file after any changes you make and restart the software. For
further information check the software manual.
