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Figure 23.33 Single and Double Ended Inputs

Signals from transducers are typically too small to be read by a normal analog input card. Amplifiers are used to increase the magnitude of these signals. An example of a single ended signal amplifier is shown in Figure 23.34. The amplifier is in an inverting configuration, so the output will have an opposite sign from the input. Adjustments are provided for gain and offset adjustments.

Note: op-amps are used in this section to implement the amplifiers because they are inexpensive, common, and well suited to simple design and construction projects. When purchasing a commercial signal conditioner, the circuitry will be more complex, and include other circuitry for other factors such as temperature compensation.

continuous sensors -23.35

Rf + R

?

= --------------- g?+ offset

Vout Ri Vin

??

Figure 23.34 A Single Ended Signal Amplifier

A differential amplifier with a current input is shown in Figure 23.35. Note that Rc converts a current to a voltage. The voltage is then amplified to a larger voltage.

Figure 23.35 A Current Amplifier

continuous sensors -23.36

The circuit in Figure 23.36 will convert a differential (double ended) signal to a single ended signal. The two input op-amps are used as unity gain followers, to create a high input impedance.

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