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Use of DrDaq

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Use of DrDaq

Postby rangas2007 » Tue Apr 05, 2011 6:04 am

Dear Sir,

I am using DrDaq card of Picotech for logging data from a load cell of an Instron .The voltage available from the load cell sensor is around 50-100mv depending on the load applied. I need to amplifiy this voltage in my experiment and propose to sense it with one of the external points(EXT1, EXT2 ) ports available on the DRDaq card.The DrDaq fits into the parallel port of the PC. However because we need to plug/unplug the DrDaq before and after our experimental runs we have made arrangement (to use a M!004 cable which we will get over the next week., right now we are using a local make cable) We have made the following observations in our exptl runs

a) The voltage is sensed at the Ext1 port( using a FCC64 fitted wire) without the amplifier i.e direct mV from the output point of the load cell sensor ( in this run the DrDaq card was directly fitted to the parallel port without the local make cable)

Following the breakdown of our PC we replaced the CPU and loaded the software again. This time we made sure that a local make cable was fitted into the parallel port at one end while we shall have the provision to plug/unplug the DrDaq card at the other end.We checked our installation in all aspects

b)We tried to amplify the load cell voltage with a simple inverting one ( using 741) and applied the same to the Ext1 port of DrDaq card But we failed in our expt after applying the settings, followed by starting to store fresh data. It indicated a data field of
xxxx

So we could not log the data.

c) We assumed that the EXt1 port must have got spoilt and applied the voltage to the voltage sensing pins of the Dr.Daq card. This time the settings were accepted and a constant voltage was logged ( 4-15mv) at My Voltage.(Actually we expect the voltage to increase over a 1-2 V span depending on our amplifier gain -within the limit of 5V
)


We are unable to figure out why the Ext1 port could not log our amplifier output.We need to connect the voltage from another sensor at MyVoltage port and we need to get the card to sense both the voltage ( one applied at Myvoltage and also the load cell output at Ext1 port) simultaneously eventually.

a)Can you suggest any particular opamp that we need to used for interfacing with the DrDaq card and load cell output ?
b)Is our problem related to the connecting of a local make cable between the port of the Pc and the DrDaq card.

c)Will our problem get solved by the M1004 cable?


Kindly reply on urgent basis,


Thanking you,

Yours faithfully,

B.Sobha
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rangas2007
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Re: Use of DrDaq

Postby ziko » Wed Apr 06, 2011 10:55 am

Hi,

Have you used a sense resistor?

External Inputs
Each external input socket has four connections:

Pin 1 Input channel with 100k pull-up to 2.5 V
Pin 2 Ground
Pin 3 Sensor type detect with 100k pull-up to 2.5 V
Pin 4 Power approx 2mA at 3-5V

Kind regards
Ziko

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Re: Use of DrDaq--urgent

Postby rangas2007 » Wed Apr 27, 2011 11:49 am

Dear Sir,

Yes , I have placed a sense resistor of 3.3 K ohm and have incorporated the following .dds file into the picolog executable directory-C://program files/pIco/Picofull'....as suggested by Mr Peter French.We connected only a single voltage of 2V to be sensed at the external ports. The connections to the FCC68 cable are

Pin1--Signal input---2V , Pin2 and 3 --3.3K ohms sense resistor , pin 4 --left unconnected on advice from Mr Peter

[Scale1]
Resistor=3.3
LongName=Custom Voltage 1
Units=Volts
MinValue=0
MaxValue=5.0
OutOfRange=0
Places=3
Method=0
NoOfPoints=2
Raw1=0
Scaled1=0
Raw2=2.5
Scaled2=5.0

When going about doing the New settings we had the problem under parameter options-->scaling---->use scaling from file------>displays---> C:// ....//picofull/Ext1 custom voltage . On clicking OK we get the message " The scaling method was not valid .---> not accepted as win32application.

What more function calls must be incorporated for the file to be recognised.
We tried again adding the following function on the top of the above mentioned software file.
PREF1 short PREF2 drdaq_open_unit (
short port);

But the data fileld logged is 'xxxxxx'' volts.


KIndly help out on urgent basis.



Thanking you,

B.Sobha
rangas2007
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Re: Use of DrDaq

Postby ziko » Tue May 03, 2011 4:26 pm

Hi you do not need to go into scaling this is for other products, for the DrDaq you just go into your input channels, choose the channel to be External 1 or 2 depending on which one is connected. The scaling will then automatically come up on the Scaling option below.

Your sense resistor will be between pin 2 and 3 and your input voltage will be between pin 1 and 2.

Hope this helps.

Kind regardsd
Ziko

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Re: Use of DrDaq

Postby sbath2000 » Wed May 04, 2011 9:35 am

Dear Sir,

I have noticed that the scaroll down menu in the scaling option box does not display any paramaeter field to choose from--this seems to be the point where the problem with settings is starting.And also the reason why we get the data logeed field as '''xxxxx''. We connected the sense resisitor and also incorporated the .dds file. Can't figure out why the scaling is failing

B.sobha
sbath2000
 

Re: Use of DrDaq

Postby ziko » Wed May 04, 2011 4:56 pm

Hi that is odd as I recreated the exact test, I was using 5.21.2. It could be taht your resistor value is not correct. Can you double check this, or that the resistor is not securely connected between pins 2 an 3.

Kind regards
Ziko

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Re: Use of DrDaq

Postby sbath2000 » Wed May 11, 2011 6:54 am

Dear Mr. Ziko,

I have measured my resstor and I find it to be 3.3K inserted between pin 2 and 3 of the FCC68 cable connected to the DaQ. Furthur I have created the .txt file file (in notepad )of External volts .dds and and placed it in Pico Full Directory, after changing the extension from txt to .dds.I hope this procedure for file insertion is okay. If not guide please

A 2.4 dc voltage was applied between pins 1 and 2 through a 1 kohm resistor , a 3.3 K ohm resistor was placed between pin 3 and pin 2, while pin 4 was left unconnected.( Is this okay??)After choosing the External port 2 entering custom voltage 1 , the scroll down menu bar under the scaling box was empty. We went to option parameters and entered volts to be sensed. I am attaching below the file contents recorded using Picolog software that we have got.


Time External 2 custom voltage 1
Seconds %

0 128.1
1 128.1
2 128.1
3 128.1
4 128.1
5 128.1
6 128.1
7 128.1
8 128.1
9 128.1
10 128.1
11 128.1
12 128.1
13 128.1
14 128.1
15 128.1
16 128.1
17 128.1
18 128.1
19 128.1
20 128.1
21 254.4
22 ******
23 ******
24 ******
25 ******
26 ******
27 ******
28 ******
29 ******
30 ******
31 ******
32 ******
33 ******
34 ******
35 ******
36 ******
37 ******
38 ******
39 ******
40 ******
41 ******
42 ******
43 ******
44 ******
45 ******
46 ******
47 ******
48 ******
49 ******
50 ******
51 ******
52 ******
53 ******
54 ******
55 ******


We measured following voltages roughly for an signal input voltage of 2.3V

Between gnd and auto detect resistor at pin 3 -- -1.56 V
Between gnd and unconnected pin 4 -------------------- 1.55 V
Between gnd and pin 1 ------------------------ 1.64 V

Furthur
b)I came across this message in Picotech forums which I attach with this letter

((((I am writing an application using visual basic. I am attempting to access external sensors but although I have created a DDS file that is read by picoscope and picolog how do I include this in my code ? Does the DLL automatically look for the DDS file or do I need to reference it somehow ?

Looking forward to the replies folks.

Regards

The .dds scaling file is automatically loaded in via the .dll functions, when the unit is first opened.

drdaq_open_unit

If more than one scaling file is provided for the sensor then you will have to use the following functions:

drdaq_get_scalings
drdaq_set_scaling

The way that the appropriate files are found is by the resistor placed between pin 3 (auto detect) and pin 2 (gnd) on the sensor. The value of the resistor is then put into the scaling file. The sacling file that matches the resistor will be loaded.

Best regards,)))))
.
c) Kindly clarify if I also need to add the following to my programme

drdaq_open_unit

If more than one scaling file is provided for the sensor then you will have to use the following functions:

drdaq_get_scalings
drdaq_set_scaling



I request to go through my mail messages I' ve written today and advice on urgent basis. I am not able to figure out where is the error.The file is still not being sensed






Thanking you,


B.Sobha
sbath2000
 

Re: Use of DrDaq

Postby sbath2000 » Wed May 11, 2011 7:04 am

Dear Sir,

Yes I have confirmed that the value of the resistor attached is 3.3kohms between the pins 2 & 3. I request you to go through the contents below and advice me .

I have created the .txt file(in notepad) of External volts .dds and and placed it in Pico Full Directory. after changing the extension from txt to .dds.

A 2.4 dc voltage was applied between pins 1 and 2 through a 1 kohm resistor , a 3.3 K ohm resistor was placed between pin 3 and pin 2, while pin 4 was left unconnected( Is this okay?).After choosing the External port 2 entering custom voltage 1 , the scroll down menu bar under the scaling box was empty. We went to option parameters and entered volts to be sensed. I am attaching below the file that we have got.

We measured following voltages roughly for an signal input voltage of 2.3V

Between gnd and auto detect resistor at pin 3 -- -1.56 V
Between gnd and unconnected pin 4 -------------------- 1.55 V
Between gnd and pin 1 ------------------------ 1.64 V

I request to go through my mail messages I' ve written today ( 2 including this with files attached) and
guide me as to where the error is.

Thanking you,

B.Sobha



Thanking you,


B.Sobha
NONAME1.PLW
This is the data file we got .
(20.6 KiB) Downloaded 202 times
dds file.doc
This letter I refer above and I have got this from Picotech forums
(26 KiB) Downloaded 191 times
sbath2000
 

Re: Use of DrDaq

Postby ziko » Thu May 12, 2011 4:44 pm

Hi can you try this attachement to see if it works?

Kind regards

Ziko
Attachments
drdaq.dds
(178 Bytes) Downloaded 204 times
Ziko

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Re: Use of DrDaq

Postby sbath2000 » Mon May 16, 2011 12:28 pm

Dear Sir,

I have downloaded the drdaq.dds file that you have kindly sent as an attachment. I am already this same file and I have
mentioned about this point in my earlier message.I have compared step by step and find that the programme drdaq.ddsis similar in all respects.Can you kindly go through my earlier message and help me out with the Drdaq sensing problem.

Thanking you,

B.Sobha
sbath2000
 

Re: Use of DrDaq

Postby ziko » Tue May 17, 2011 3:29 pm

Hi Sobha,

I have emailed you with some information on the helpdesk.

Kind regards
Ziko

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Re: Use of DrDaq

Postby sbath2000 » Fri Jun 03, 2011 10:09 am

Dear Mr. Ziko,

We have tried out the .dds file you sent to us. However we have been facing a problem of extreme summer temperatures ( approx 45 C) over the past twenty days and more. Right now the software is not recognising the DrDaq device and gives a messsage "DrDaq not found on ..., "/DRiver V3.7 not found/ unable to locate pico.sys."We have tried uninstalling and installation of the software but the recogniion problem continues. Please clarify if the extreme temperatures are responsible for the malfunctioning of the device.

Thanking you,

B.Sobha
sbath2000
 


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