Lines Term, Control, and 4.75V are data and power outputs, respectively. They will be discussed in the
next section »Data Outputs«. Lines PL, S/E, and Ext can be regarded as data inputs when using the
6150AD as a ratemeter for external probes. Data inputs will be covered in the appendix »Data Inputs«.
However, this appendix contains confidential information and will be added to this document only on
special request.
2. Data Outputs
2.1 »Term«
The 6150AD calculates a new dose rate value approximately every second and outputs this value as a
string of characters through the Term line. This can be used to read the 6150AD by a computer through a
serial RS232 interface. Output characters are binary and thereby not suitable to be viewed directly on a
serial terminal or printer. The time between two subsequent output strings may vary slightly due to
varying microprocessor load. Nevertheless, counting strings may also be used for time measurement,
since the average time between two strings is exactly equal to 1.049 seconds (2
20
µs) as derived from the
internal quartz.
Term acts purely as a transmitter, there is no way to feed data into the 6150AD or to request a repeat in
case of transmission errors. Also, there are no handshake signals to control the Term output.
2.1.1 Hardware Characteristics
The Term line is a CMOS gate output with an impedance of several hundred Ohms. Its driving
capability is therefore at least equivalent to RS232 interfaces. Nevertheless, cables should be restricted to
maximum lengths as with RS232 interfaces (15m at 9600Bd, 30m at 4800Bd, etc.). Contrary to RS232
lines the Term output is not short circuit proof and swings between GND and 4.75V because there is no
negative voltage available in the 6150AD.
Term output RS232 output specs RS232 input specs
logical »0«:
+4.75V
+5...+15V
> +3V
logical »1« (marking state): GND
-5...-15V
< -3V
Although the positive Term level of 4.75V does not completely meet the RS232 specification of +5V
minimum, it should be properly recognized by any RS232 device, since any voltage above +3V has to be
recognized as the positive level. The GND level however lies in the undefined range from -3V...+3V.
Fortunately almost all RS232 devices recognize GND level as the negative level. So far we only met one
exception in a many years old IBM serial/parallel adapter using a 75154 input buffer. This input buffer
changes and stores its state only if its input level is outside the -3V...+3V range. If this rare case should
occur, the remedy would be to feed Term through a 1 nF capacitor into the RS232 interface. This
capacitor will differentiate GND to +4.75V and +4.75V to GND transitions to positive and negative
spikes, which will be recognized and stored by the 75154.
06/2003
Technical Manual 6150AD Probe Connector
Page 3 of 14
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