# Finding an Analog Multiplexer for Accurate Voltage Measurements

• BillyBobjoe
In summary, the conversation discusses the use of an analog MUX to select and switch through multiple input voltages onto a single input ADC. The importance of accuracy in voltage measurements and the possibility of using the MUX as a sample-and-hold circuit is also mentioned. Different manufacturers are suggested for finding suitable analog MUXes.
BillyBobjoe
Hi

I need to take in a number of analog voltages onto an ADC but the ADC is a single input. I was thinking of putting the voltages through a MUX and then selecting the input desired to go to the output of the MUX and onto the ADC.

Does anyone know of good analog MUX's/Switches that will allow the desired voltage on the input of the MUX to be selected to go to the output.

My voltage measurements need to be accurate so the input voltage on the MUX must also be seen at the output.

Or is there another way i could go about switching through my voltages into the single input ADC.

Thanks

BillyBobjoe said:
Hi

I need to take in a number of analog voltages onto an ADC but the ADC is a single input. I was thinking of putting the voltages through a MUX and then selecting the input desired to go to the output of the MUX and onto the ADC.

Does anyone know of good analog MUX's/Switches that will allow the desired voltage on the input of the MUX to be selected to go to the output.

My voltage measurements need to be accurate so the input voltage on the MUX must also be seen at the output.

Or is there another way i could go about switching through my voltages into the single input ADC.

Thanks

Does your ADC already have a sample-and-hold circuit? If not, you would use the analog mux as the S/H as well as the mux.

Just google analog mux, and you will get lots of good hits. Linear Technology, Maxim, Analog Devices, National Semiconductor all make them. You will pay more for switches with lower ON resistances, so you need to figure out your S/H circuit, including the capacitor value and how fast you want to sample, and how long you want to hold. That will help you choose the ON resistance and OFF leakage current specs to use in picking the device.

for reaching out about your project! It sounds like using an analog multiplexer is a great solution for your needs. There are many different types of MUX's available, so it's important to consider your specific requirements when selecting one. Here are some factors to keep in mind:

1. Accuracy: As you mentioned, accuracy is crucial for your voltage measurements. Look for a MUX with a high precision and low crosstalk between channels.

2. Input and output voltage range: Make sure the MUX you choose can handle the voltage range of your inputs and outputs.

3. Number of channels: Consider the number of channels you need. MUX's can range from a few channels to dozens, so choose one that fits your specific needs.

4. Switching speed: If you need to switch between channels quickly, look for a MUX with a fast switching speed.

5. Compatibility with your ADC: Ensure that the MUX you select is compatible with your ADC in terms of voltage levels and communication protocols.

Some popular MUX's for accurate voltage measurements include the ADG1401 and the MAX4618. It's always a good idea to consult with a supplier or manufacturer to find the best fit for your project. Good luck with your measurements!

## 1. What is an analog multiplexer and why is it used for voltage measurements?

An analog multiplexer is a device that allows multiple analog signals to be selected and routed to a single output. It is used for voltage measurements because it can switch between different input channels, allowing for accurate and efficient measurement of multiple voltage sources.

## 2. How do I choose the right analog multiplexer for accurate voltage measurements?

There are several factors to consider when choosing an analog multiplexer for accurate voltage measurements, including the number of input channels, the input signal range, the switching speed, and the accuracy and resolution of the device. It is important to carefully evaluate these specifications to ensure that the multiplexer can meet the requirements of your specific voltage measurement application.

## 3. What are some common sources of error in voltage measurements using an analog multiplexer?

Some common sources of error in voltage measurements using an analog multiplexer include signal cross-talk, channel leakage, and non-linearity in the switching elements. It is important to carefully design the circuit and select a high-quality multiplexer to minimize these sources of error.

## 4. Can I use an analog multiplexer for both AC and DC voltage measurements?

Yes, there are analog multiplexers available that can handle both AC and DC voltage measurements. However, it is important to carefully evaluate the specifications of the device to ensure that it can accurately and reliably measure both types of signals.

## 5. What are some key features to look for in an analog multiplexer for accurate voltage measurements?

Some key features to look for in an analog multiplexer for accurate voltage measurements include low on-resistance, high off-isolation, low channel leakage, and low distortion. Additionally, it is important to consider the device's packaging, power consumption, and temperature range to ensure it is suitable for your specific application.

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