Product question(USB 2.0 DATA ACQUISITION SYSTEM)

[KS Liu]

Hi Team

 

My customer encountering a strange issue, he is using a photodiode system from Thorlabs, which is confirmed to output analog signal. However, he will see display showing 10V outrange as connecting to channel. Other signals are fine, like 1.6 V battery output.

please see attached file and also videos. could you please help check if there is anything weird from connections?

 

USB-1608FS-Plus_Issue.docx

[KS Liu]

Hi Team

do you have any feedback for the issue I asked yesterday, it is really urgent for customer to utilize your product

I missed the third video and added for you

thank you

 

[Fausto]

Hello @KS Liu.

Please disconnect all signal wires to the USB-1608FS-Plus analog input channels.  Afterward, wire terminal 39 (PC +5V) over to terminal 1 (CH0 IN) and wire terminal 40 (GND) over to terminal 20 (AGND).  Open DAQami and enable analog input channel 0 (AI0) only.  Run the acquisition.  Does the measurement show approximately +5 V?  If it does, stop the acquisition, disable analog input channel 0, and enable analog input channel 1 (AI1) only.  Disconnect the physical wire from screw terminal 1 and reconnect the wire to screw terminal 3 (CH1 IN).  Run the acquisition in DAQami.  Does the measurement show approximately +5 V?  If it does, stop the acquisition and repeat the previous steps for the remaining analog input channels.  If the measurements were not as expected, then the USB-1608FS-Plus device is damaged and should be replaced with another USB-1608FS-Plus device.

If all eight channels measured approximately +5 V, then the USB-1608FS-Plus device is functioning correctly.  Disconnect the current wiring on the device and connect the photodiode system from Thorlabs to terminal 1 (CH0 IN) and terminal 2 (AGND).  Reconfigure the channel in DAQami and retest the acquisition.

If the measurements from the USB-1608FS-Plus device continue to show 10 V, then the DC bias input voltage to the PBM42 module may be the root cause.  Disconnect the phono plug cable to the PBM42 module and repeat the acquisition in DAQami.  Does the data continue to show 10 V?  If it does not, then we need to investigate the DC bias input signal.

Regards,

Fausto

 

[KS Liu]

Hi Fausto

 

Thank you so much for your comments, here is feedback from customer, please see content with underline

Based on MCC’s reply, we do the DOE below:

Please disconnect all signal wires to the USB-1608FS-Plus analog input channels.  Afterward, wire terminal 39 (PC +5V) over to terminal 1 (CH0 IN) and wire terminal 40 (GND) over to terminal 20 (AGND).  Open DAQami and enable analog input channel 0 (AI0) only.  Run the acquisition.  Does the measurement show approximately +5 V?  If it does, stop the acquisition, disable analog input channel 0, and enable analog input channel 1 (AI1) only.  Disconnect the physical wire from screw terminal 1 and reconnect the wire to screw terminal 3 (CH1 IN).  Run the acquisition in DAQami.  Does the measurement show approximately +5 V?  If it does, stop the acquisition and repeat the previous steps for the remaining analog input channels.  If the measurements were not as expected, then the USB-1608FS-Plus device is damaged and should be replaced with another USB-1608FS-Plus device.

---AI0，AI2，…AI7 around 5.06V.

If all eight channels measured approximately +5 V, then the USB-1608FS-Plus device is functioning correctly.  Disconnect the current wiring on the device and connect the photodiode system from Thorlabs to terminal 1 (CH0 IN) and terminal 2 (AGND).  Reconfigure the channel in DAQami and retest the acquisition.

If the measurements from the USB-1608FS-Plus device continue to show 10 V, then the DC bias input voltage to the PBM42 module may be the root cause.  Disconnect the phono plug cable to the PBM42 module and repeat the acquisition in DAQami.  Does the data continue to show 10 V?  If it does not, then we need to investigate the DC bias input signal.

Connect the 12V power supply of PBM42, DAQ readings 10V; Disconnect the 12 V power supply, DAQ readings 10V.

 

We test NR-500+NR-HA08 of Keyence, it works well when replacing USB-1608FS-Plus. And as show in videos, we have already test thorlabs’ system by multimeter, KEITHLEY 3706A, they all work well.

I think basically USB-1608FS-Plus has no issue itself, but it is probably not suitable for this configuration, maybe the input impendence or inner circuit are different from others. I am not sure about whether the DAQ should be a individual circuit which only measure voltage between terminal 1 and terminal2.

Based on thorlabs’s reply, their system should add a high load resistance to match USB-1608FS-Plus’s impendence. But we haven’t test it yet. Hope you can suggest it on the whole circuit if you know about the photodiode system.

[Fausto]

Hello @KS Liu.

Thank you for the responses.

The USB-1608FS-Plus device has an analog input impedance of 100 MΩ min.  Typical signal connections to our daq devices have an impedance <1000 Ω.

For some customer applications, the input voltage to a data acquisition device comes from a high impedance source.  In this situation, it is necessary to introduce an operational amplifier (op amp) between the voltage source and the daq device's voltage input channel.

Does that suggestion resolve the issue?

Regards,

Fausto