"Glenn Ashmore" wrote in message
news:SuTJd.23349$EG1.9142@lakeread04...
I have gotten an extraudinary deal on a really nice flow transducer that
will make a great remote product readout for my watermaker. The problem
is
that it has sinking and sourcing outputs. I want to use it for input to
an
LM2907 frequency to voltage converter but the LM2907 requires a crossing
voltage from positive to negative for the pulses. How do you turn a
positive to zero pulse into a positive to negative pulse when you only
have
12V+ to work with?

That depends on which LM2907 you have: the 8 pin version has one input of
the comparator grounded so the other needs a read AC voltage. Here you can
connect a resistor of 100k from input to ground and couple the output of the
flow transducer to the input with a capacitor of 10uF. This may be an
electrolythic type, with the plus to the transducer and the minus to the
LM2907 input/resistor. This will create a true AC voltage on the input of
the LM2907.

If you have the 14 pin version of the LM2907, you can put the inverting
input at half VCC with a voltage divider: two resistors of 10k in series
between 12V and ground and the "middle" connected to the inverting input of
the LM2907. Bypass the this input to ground with a 10uF elco. The sensor
output can then be connected directly to the non-inverting input op the
LM2907.

Regards,
Meindert