LabJack U3 User Manual
                                                                                                                        | |
Contents
| 
Figure 2-3. Voltage Divider CircuitThe attenuation of this circuit is determined by the equation:his divider is easily implemented by putting a resistor (R1) in series with the signal wire, andterminal. To maintain specifiednalog input performance, R1 should not exceed 10 kΩ, so R1 can generally be fixed at 10 kΩe desired attenuation. For instance, R2 = 9.1 kΩ provides aivide by 2.1, so a ~0-5 volt input will be scaled to the input range of the U3.Thegured as non-verting unity-gain (i.e. a buffer).Vout = Vin * ( R2 / (R1+R2))Tplacing a second resistor (R2) from the AIN terminal to a GNDaand R2 can be adjusted for thdThe divide by 2 configuration where R1 = R2 = 10 kΩ, presents a 20 kΩ load to the source,meaning that a 5 volt signal will have to be able to source/sink up to + 250 μA. Some signalsources might require a load with higher resistance, in which case a buffer should be used.following figure shows a resistive voltage divider followed by an op-amp confiinFigure 2-4. Buffered Voltage Divider CircuitThe op-amp is chosen to have low input bias currents so that large resistors can be used in thevoltage divider. For 0-5 volt applications, where the amp will be powered from Vs and GND, aas Instruments (ti.com). The OPA344 has a verythe entire voltage range. Note that when poweringe amp from Vs and GND, the input and output to the op-amp is limited to that range, so if Vs isnown resistance.good choice would be the OPA344 from Texsmall bias current that changes little acrossth4.8 volts your signal range will be 0-4.8 volts.The information above also applies to resistance measurement. A common way to measureresistance is to build a voltage divider as shown in Figure 2-4, where one of the resistors isknown and the other is the unknown. If Vin is known and Vout is measured, the voltage dividerequation can be rearranged to solve for the unk21 |
This manual is suitable for:
manualsdatabase
Your AI-powered manual search engine