Chapter 3
Adapting Transducers
37
You will need the following equipment:
•
a soldering iron and resin-cored solder (ONLY resin-cored solder)
•
an eight-pin DIN-style male plug with 45-degree pin spacing
(supplied with your Bridge Amp)
•
common E12 resistors: 0.25 or 0.125 Watt, 2% or 1% metal film.
Setting the Excitation Voltage
The first step in preparing a powered transducer for use with the
Bridge Amps is to set the required excitation voltage. Two of the pins
in the Bridge Amp’s DIN socket can provide up to 20 volts DC as
excitation voltage to power the transducer. The voltage is varied by a
resistor fitted between the two corresponding pins of the transducer’s
DIN plug. When no resistor is present, the Bridge Amp’s internal
circuitry cuts off all voltage to prevent mishaps. Once a resistor is
fitted, the correct excitation voltage is provided automatically when
the transducer is plugged into the Bridge Amp.
To program the excitation voltage for a particular transducer, choose a
value of resistance from Table 3–1 to match the required excitation
voltage for your transducer. In most cases, you should be able to get
close to the required excitation voltage by selecting one of those
values. We recommend that the excitation resistor be 0.25 or 0.125
Watt, 2% or 1% metal film. Larger resistors may not fit in the confined
space of the transducer’s DIN plug.
In general, the output voltage from the transducer is directly
proportional to the excitation voltage placed across it. The greater the
excitation voltage, the more sensitive the transducer becomes.
Excitation voltage
(DC volts)
Excitation
resistance
(
Ω
)
Excitation voltage
(DC volts)
Excitation
resistance
(
Ω
)
20
Short circuit
5
470 k
18
12 k
4
560 k
15
47 k
3.5
680 k
12
100 k
3
820 k
10
150 k
2.5
1 M
8
220 k
2
1.2 M
6
330 k
Table 3–1
Transducer excitation
voltage and resistance
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