050326-1457 EST USA
Some additional information.
If when you are in the short circuit test condition you also send data the average
should be less than 1 MA during data transfer. The reason that both voltage and
current are near zero when sending data is that on average for random straight
text the number of + bits is approximately equal to the number of - bits. For example
if you sent only the NULL ASCII character which is all zeroes ( using 7 bits ), no
parity, and 1 stop bit, then the data stream at pin 2 would be 8 zero bits and 1 one
bit. This is a duty cycle of 1/9. Since a data bit 0 maps to a + bit at pin 2 this means
your average would be about (8/9)x12 = 10.6 V. But straight text does a pretty good
job of averaging zeros and ones.
On a HAAS VF2 (1993) with a Simpson 270 I read about +0.2 MA when sending data
vs -9.8 MA in the idle state. On a Model 27 Fluke the average DC voltage during data
transfer was about 1 to 1.5 V compared to about 0.6 V on the Simpson. The average
current reading on the Fluke was about 0.3 to 0.4 MA compared to the Simpson of
0.2 MA. These tests were at 38.4 Kbaud.
At 9600 baud the Fluke was considerably noisier then the Simpson on voltage, but
about the same on current.
The data transfer tests are useful because they verify that both + and -
sides of the driver are working.
All our HAAS machines have the same RS232 pinout and this is generally the same
as Fanuc.
cadcam if you were responding to our post, then our location is Ann Arbor,
Michigan and our web site is
www.beta-a2.com. We are about 3/4 mile from the
U of M Stadium which is generally packed with close to 110,000 on football days
and if the weather is wet we end up a large number of cars in our parking lot.
We have 5 HAAS machines dating from 1993 thru 2000. HAAS machines make RS232
communication very easy, and also allow high baud rates ( 38.4 Kbaud on older models
and 115.2 Kbaud on newer ones ). We can send about 600,000 bytes per minute at
the 115.2 Kbaud rate.
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