Badger Meter 106-255 - Manual (Page 2)

Model 106-255 Signal Conditioner, Modulated Carrier, Meter Mounted
2
Selection of the power supply level and series resistor
value in Figure 1A is not critical, however, certain
guidelines should be followed. The signal conditioner
is designed to operate at supply voltages between 15
and 28 volts DC. The maximum current drawn by the
signal conditioner is determined by the selection of
power supply voltage and resistor. A supply with a
minimum output current capability of 100 milli-
amperes should be provided to assure stable signal
output. The resistor value selected should not be so
large as to limit operating current to the signal
conditioner. Figure 3 graphs the maximum resistor
vs. supply voltage. In using this graph, select the
minimum expected value of supply voltage and read
the corresponding maximum value that may be
selected for the series resistor. For example, if the
minimum expected supply output is 22 volts, the
maximum valued resistor that should be used is
approximately 330 ohms. For most installations, a 1
watt carbon composition resistor will be adequate.
Figure 4 gives the output peak to peak voltage vs. the
series resistor value for a range of power supply
voltages. The shaded area to the left exceeds the
maximum resistor selection and is excluded from the
useable range. Figure 5 provides the minimum value
signal excursion or DC component. Peak to peak and
minimum signal are illustrated in Figure 2.
The jumper indicated between terminals “O” and “C”
is required for proper output. This connection enables
the internal switching transistor which produces the
modulation of the supply current.
THREE WIRE INTERFACE
The Three Wire Interface illustrated in Figure 1B
provides an output signal which can be directly
connected to counters or indicators defined as being
TTL compatible. Unlike the signal output from the
Two Wire Interface, the signal output from this
configuration will provide a near zero minimum signal
excursion. The maximum or peak output signal is
determined by the user. An additional wire is required
and, depending on the requirements of the external
system, a second power supply level may be needed.
As in the two wire interface, the flowmeter pick-off is
connected directly to terminals “A” and “B”. The
power supply required can be at any voltage level
between 15 and 28 volts and should be capable of
supplying a minimum 100 milli-amperes. This is
connected directly to terminals “+” and “-“ as
illustrated.
No connection is made to terminal “O”. Terminal
“C” provides the output signal to the frequency
counter or rate indicator. As this output is from an
“open collector” source, a pull-up resistor Rp is
required. The pull-up resistor must be connected to a
positive supply level generally equal to the maximum
desired signal excursion. If interfacing directly to logic
Figure 2. Typical output signal for the Two Wire Connection.
V
min
is a positive level on which the signal rides. V
p-p
is the
peak to peak swing of the output signal.
Figure 3. Maximum value for R
series
in ohms vs. power
supply voltage.