Please select a DAQ suitable for our research

[yaaan]

We are planning to conduct an experiment to collect bioelectric signals from plants. These signals are approximately ±0.2 mV, and we are considering a sampling rate of around 500 Hz. When collecting the electrical signals, we plan to insert electrodes directly into the plants. We would like to know what suitable DAQ equipment is available and what type of DAQ equipment would be best to use.

Thank you for taking the time to help us with this.

[Henrik_Volkers · Accepted solution]

How many channels do you want to read?

I assume a high input impedance is needed? >1MOhm or >1GOhm ?? 

Noise? Resolution?

max Bias current?

+-200µV range isn't that much, my first thought was a nV Meter like Keithley 182 or 2182, but these specialist don't read that fast.

Other points:

Electrodes, cables and temperature (abs & gradients)  will be of great influence, well and EMC conditions  😉

Maybe a bridge DAQ like the 9219 (max 100Hz SR) or alike with ranges in the tens of mV are possible candidates.

Before buying I strongly recommend to test the equipment.

Another approach would be to use preamplifiers.

[Bob_Schor · Accepted solution]

As someone who has measured bio-electric signals, the recording electrode is almost always connected to an amplifier that (if nothing else) provides impedance-matching between the electrode (which can be in meg-ohms) and the recording equipment.  Assuming that this is the case, and given the rather modest sampling rates you are employing, you may do quite well with one of NI's multi-function USB DAQ devices.

Bob Schor

[santo_13 · Accepted solution]

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@yaaan wrote:

We are planning to conduct an experiment to collect bioelectric signals from plants. These signals are approximately ±0.2 mV, and we are considering a sampling rate of around 500 Hz. When collecting the electrical signals, we plan to insert electrodes directly into the plants. We would like to know what suitable DAQ equipment is available and what type of DAQ equipment would be best to use.

Thank you for taking the time to help us with this.

---

+/-0.2mV is a very small signal typically riddled with noise for more low-cost DAQ. If you can add an amplifier to bring it to the +/-5V range, you've a wider range of options.

[NIquist · Accepted solution]

I agree with all the comment above.  The DAQ is mostly irrelevant compared to the need for good signal conditioning in this application.

[yaaan]

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@santo_13  작성:

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@yaaan wrote:

We are planning to conduct an experiment to collect bioelectric signals from plants. These signals are approximately ±0.2 mV, and we are considering a sampling rate of around 500 Hz. When collecting the electrical signals, we plan to insert electrodes directly into the plants. We would like to know what suitable DAQ equipment is available and what type of DAQ equipment would be best to use.

Thank you for taking the time to help us with this.

---

+/-0.2mV is a very small signal typically riddled with noise for more low-cost DAQ. If you can add an amplifier to bring it to the +/-5V range, you've a wider range of options.

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Are you referring to the construction of an additional amplification circuit when you mention adding an amplifier?

[yaaan]

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@Henrik_Volkers  작성:

How many channels do you want to read?

I assume a high input impedance is needed? >1MOhm or >1GOhm ?? 

Noise? Resolution?

max Bias current?

+-200µV range isn't that much, my first thought was a nV Meter like Keithley 182 or 2182, but these specialist don't read that fast.

Other points:

Electrodes, cables and temperature (abs & gradients)  will be of great influence, well and EMC conditions  😉

Maybe a bridge DAQ like the 9219 (max 100Hz SR) or alike with ranges in the tens of mV are possible candidates.

Before buying I strongly recommend to test the equipment.

Another approach would be to use preamplifiers.

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The number of channels doesn't matter much, but the noise must be minimized, and the resolution must be high. The price is not a major concern, and if an amplifier is needed, I would appreciate your guidance on what framework would be required.

[yaaan]

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@Bob_Schor  작성:

As someone who has measured bio-electric signals, the recording electrode is almost always connected to an amplifier that (if nothing else) provides impedance-matching between the electrode (which can be in meg-ohms) and the recording equipment.  Assuming that this is the case, and given the rather modest sampling rates you are employing, you may do quite well with one of NI's multi-function USB DAQ devices.

Bob Schor

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Could you let me know which circuits, devices, or components you have used in the process of amplifying recording electrodes? Thank you.

[santo_13 · Accepted solution]

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@yaaan wrote:

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@santo_13  작성:

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@yaaan wrote:

We are planning to conduct an experiment to collect bioelectric signals from plants. These signals are approximately ±0.2 mV, and we are considering a sampling rate of around 500 Hz. When collecting the electrical signals, we plan to insert electrodes directly into the plants. We would like to know what suitable DAQ equipment is available and what type of DAQ equipment would be best to use.

Thank you for taking the time to help us with this.

---

+/-0.2mV is a very small signal typically riddled with noise for more low-cost DAQ. If you can add an amplifier to bring it to the +/-5V range, you've a wider range of options.

---

Are you referring to the construction of an additional amplification circuit when you mention adding an amplifier?

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Yes, one can generalize it as signal conditioning, typically it is amplification and may be paired with filtering as well.

[yaaan]

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@NIquist  작성:

I agree with all the comment above.  The DAQ is mostly irrelevant compared to the need for good signal conditioning in this application.

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In the process of plant -> amplification -> DAQ -> data collection, does this mean that the scaling process in the application is more important?