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DETERMINING MEASUREMENT ACCURACY

by Hristo Stefanov

Start ý Defining the Terms ý A Little Theory ý Sources of Error ý Error Budget ý Error Budget Example ý Offset and Gain Errors ý Sources and PDF

ERROR BUDGET EXAMPLE

The well-known noninverting amplifier based on a single op-amp is used to demonstrate the error budget approach (see Figure 1).

The characteristics of the amplifier are:

ý maximum input voltage:

ý maximum output voltage:

ý nominal gain: G = 100

ý transfer function: V_OUT = GV_IN

Thereýs an infinite number of error sources that degrade the circuit performance. Take into account those that cause considerable error. The primary sources of errors come from op-amps and resistors in the feedback. You can get the data required for building the error budget from the componentsý worst-case specifications.

The electrical characteristics of the op-amp (the OP177 from Analog Devices) can be seen in Table 1. For the resistors, the temperature coefficient is ± 50 ppm and the tolerance is ± 1%.

Table 1ýHere you can see the electrical characteristics of the OP177 op-amp.

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