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Measuring voltages using external sensor port

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Measuring voltages using external sensor port

Postby KEX » Wed Aug 17, 2011 8:18 pm

Would someone review this to make sure I have the correct understanding of the external input connector FCC68 plugs on DrDAQ. I am trying to build an external sensor to measure AA battery voltages (0-1.5V).

+AAbattery-
|................|
|--ResistrA--|--ResistrB--
|................|................|
1...............2...............3

Numbers 1,2,3 represent DrDaq external sensor connectors.
1. What Resistor specs (Ohms) should I use so that the external sensor will be recognized my software?
2. Is Resistor B necessary for the sensor to be recognized?
Thank you for any guidance.
KEX
 

Re: Measuring voltages using external sensor port

Postby PeterF » Fri Aug 19, 2011 12:25 pm

Hi Kex,
Assuming you are using a USB DrDaq:-
You must have one of the fixed resistors fitted between pins 2 & 3 to tell the DrDaq which scaling to use. The scaling is defined by a "Scaling.dds" file which you must generate and put in the root directory of PicoLog. I attach an example file "Ext Volts.dds" which you can use as a start. If you put a 3.3kohm resistor between pins 2 & 3, that will tell PicoLog to use [Scale1], which will then give you voltage readings between 0V & 2.5V on any Ext Input that is connected.
Pages 28 to 33 & 35 to 38 in the attached USB DrDaq manual will tell you the details:-
http://www.picotech.com/document/pdf/usbdrdaq_en-1.pdf
Please contact again if you have any other questions.
Regards,
PeterF.

"Ext Volts.dds"

[Scale1]
Resistor=3.3
LongName=Voltage
Units=Volts
MinValue=0
MaxValue=2.5
OutOfRange=2
Places=3
Method=0
NoOfPoints=2
Raw1=0
Scaled1=0
Raw2=2.5
Scaled2=2.5
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Re: Measuring voltages using external sensor port

Postby Florin1234 » Thu Feb 14, 2013 1:13 pm

Hello, I would like to use DrDAQ for voltage readings between 0V and 2.5V on a Ext Input, so I tried to use the instructions given above. I still encountered some problems, after copying the "Ext Volts.dds" file into the root directory of PicoLog software, The PicoLog Recorder was no longer available, all the shortcuts automatically opened PicoLog Player. Do you have any idea of what went wrong when operating the changes? Thank you!
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Re: Measuring voltages using external sensor port

Postby PeterF » Fri Feb 15, 2013 8:10 am

Hi,
If, when running PicoLog, you minimise the Recorder window, then it will shrink to a small "PL" logo in the bottom right of the tool-bar. When you wish to restore to the original window size, just double-click on that small "PL" logo. The display will return to as before. If, at any time Recorder is running, even when minimised, you double click on the main PicoLog icon on the desk-top, then Player will start. (This will happen even if Recorder has "crashed" as it is often still running in the background. In that case, go to Windows Task manager, "Processes", highlight "plw32.exe" and click the "End Process" button.) I hope that explains.
Regards,
PeterF.
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Re: Measuring voltages using external sensor port

Postby ROLFE1234 » Wed May 07, 2014 9:18 am

Hi, continuing with this thread, I'd like to measure voltages on the external sensor port; however, the voltages in question that I will be using are between 0 and 1 volt. Would a 3.3kohm resistor still be recommended in this case between pins 2 and 3?
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Re: Measuring voltages using external sensor port

Postby PeterF » Thu May 08, 2014 7:27 am

Hi,
Yes, you would still use the 3k3 resistor and the same "Ext Volts.dds" file as before. The DrDaq will measure from 0V to +2.5V and +1.0V is within that range.
Regards,
PeterF.
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Re: Measuring voltages using external sensor port

Postby DJmilkyway » Wed Aug 20, 2014 2:39 pm

hi!

i want to measure 0 to 25 volts, i tried to figure it out with the user's manual :?
what do i need to build?
and how do i create an .ddl file?

greetz,

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Re: Measuring voltages using external sensor port

Postby Martyn » Fri Aug 22, 2014 7:40 am

Create a file, "Ext Volts.dds", using a text editor containing
Code: Select all
[Scale1]
Resistor=3.3
LongName=Voltage
Units=Volts
MinValue=0
MaxValue=25
OutOfRange=2
Places=3
Method=0
NoOfPoints=2
Raw1=0
Scaled1=0
Raw2=2.5
Scaled2=25

and ensure that you use a 10:1 voltage divider to step the input voltage down from 25V to 2.5V, and the 3.3k resistor as mentioned.
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