SCB 68 connections

I have a piezo pressure transducer connect by BNC to an amplifier, the exit is BNC and the end of the cable is open: one brings the signal the other the ground. I would like to connect it to the SCB 68 box but I have problems to identify which kind of signal source type I have - grounded signal source or floating signal source - ... (Fig. 3.1 SCB 68 manual) in order to select the best connection. I was thinking to connect the two cable one in the ACH0 and the other one in the ACH0GND? Any idea? Tks Polh

That depends on your amplifier. Is the amplifier output isolated? Does the amplifier run from the building AC supply or from batteries? If from the building AC supply, is it powered through an isolation transformer, or does it have an isolated power supply internally?
The most common situation (in my experience) is that the amplifier runs from the AC supply, and the output shield is connected to the building ground. In that case, you may be able to use the connection to ACH0 and ACH0 Gnd, but you may risk a ground loop. It may be better to use a differential input and connect your signal to ACH0 and the shield to ACH8.
Hope this helps!
John Weeks
WaveMetrics, Inc.
Phone (503) 620-3001
Fax (503) 620-6754
www.wavemetrics.com

Similar Messages

Why is AIGND on SCB-100 connected to mains earth through PCI6031E?

I have a PCI-6031E DAC card connected to an SCB-100. I am trying to measure non-referenced differential signals, and via the application notes realise that i must use two bias resistors to AIGND from the +ve and -ve terminals of each channel.
However i can't quite understand why the AIGND pin inside the SCB-100 is connected to mains earth through the DAC card. Surely any disturbances on the earth due to the operation/swiitching of other equipment on our site will produce disturbances on the reference of the DAC card, and hence effect the data that i am recording?
Or is this connection not direct, i.e through a resistor for example?
Any guidance would be much appreciated.
Many thanks
Mike

Hi,
the resistors are both tied to the same point, ergo any change in voltage on the earth line will appear on both signal lines (aix+ and aix-).
Since this is a differential input, they will be cancelled out as a common mode voltage.
The purpose of the resistors is to prevent the input voltages to the aix+ and aix- floating off. You're measuring a differential voltage, say 10V, but that could be at 50V on the aix- and 60V on the aix+. That would damage the card, and without the resistors, the signals from a true floating source could continuously float up and down.
You're quite correct in the fact that aignd is also pc or system earth, and you can get mains earth signals on this pin, hence the reason we recommend NRSE or differential as the better two input types.
http://digital.ni.com/public.nsf/websearch/1ffcbe3451abee09862562970059881d
http://digital.ni.com/public.nsf/websearch/D509679FFAE2764386256297005D0C9D
Hope that helps.
Sacha.
// it takes almost no time to rate an answer

Scb-68 connection to the building ground

Dear NI experts,
I need to measure the light emission of a laser by means of a photodiode. I have a standard desktop PC connected to a DAQ acquisition board by a USB cable. Then the DAQ is connected to a SCB-68. First question: I must perform a differential acquisition or a single referenced aquisition with a photodiode? Second question: if I chose a single referenced acqisition I need to connect the SCB-68 case directly to the building ground? Or the System PC+DAQ+SCB-68 is already connected to the ground? Sorry for my elementary questions but I not very familiar with electricity...
Thank you so much
Best regards

Hi,
If you have less than 8 signals, you should use Differential mode. This mode does not care about grounding. The only thing that you may want to do is to connect a 100 kOhm resistor between (-)terminal of your AI channel and GND, so that the signal is biased.
If you are going to need more than 8 channels, then Single Ended is the way to go for your connections.
- Referenced> use it if your sensor is connected to ground and the ground is the same as the ground for your PC
- Non Referenced> use it if your sensor is connected to a ground different from the ground of your PC or if it is not grounded.
Cheers,
AlessioD

SCB-68 connection diagram for PXI-6225

Hi,
I have to connect a PXI-6225 board to a SCB-68.
I can't find anywhere the connection diagram of SCB-68.
Anyone can help me?
Thanks,
Federico

Hi Frederico-
The SCB-68 is just a connector block- the pinout of your PXI-6225 card will map directly to the numbered pins on the SCB-68. This KB provides quick reference labels for the two connectors on your card.
Hopefully this helps-
Tom W
National Instruments

SCB 68 connections

Dear Sir
I am using NI PCI 6281 along with SCB-68. I want to collect data from a sensor which has BNC connector. My SCB 68 has no BNC port and I can only connect bare wires. What I should do? If I remove the BNC plug from the sensor wire and connect bare sensor wires to SCB 68 then will it be OK? or it will effect on the measurement?
Kind Regards
Urfee
Solved!
Go to Solution.

You may get a little more noise when going through the connector block than you would if you had a direct BNC connection on the DAQ. But it shouldn't be enough to matter. I would just cut the end off of the BNC cable to connect the signal and ground in the terminal block.
But if you are really worried about it, NI does have some DAQ boards with BNC connection. I haven't looked in a while, but they tend to be on the high end.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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PC freeze after booting with SCB 68 (connection box) connected

My PC hang immeaditely after boot when my signal box SCB 68 is connected. What can cause this error?
Can it be due to some driver problems? Wrong cable? Others who had same problem?
Rune
Test technican

Rune:
Sounds odd to me. Have you tried disconecting pieces of hardware incrementally and reboot to try and isolate the cause? Of course power down the PC while disconnecting hardware.
1. Disconnect any devices/wiring on the SCB-68
2. Disconnect the SCB-68 from the cable
3. Disconnect the cable
4. Remove DAQ card from PC.
If you still hang up during boot, then I would say it is a software issue. Let us know how 1-4 goes.
What operating system, LV and DAQ versions are you using?
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~

Can I make a simple voltage recording when SCB-68 is configured for Cold Junction Compensation?

Hi everyone,
I am using a 6221 PCI card and SCB-68 connection module. I have set the SCB-68 module switches so that the 5 thermocouples I have connected between AI1 and AI5 are using the Cold Junction Compensation of AI0. Everything works fine.
Could someone tell me if the differential inputs left AI6 and AI7 can be used for recording another kind of sensor (nothing to do with a thermocouple) ? I suppose I just need to set those 2 inputs to a simple voltage recording function? The previous switches settings enable to do this simple recording ?
Thanks,
User
Solved!
Go to Solution.

Hi Bruce,
Thanks for your answer and your advice. So I will use my free channels for other sensors.
Concerning your other remarks , I have planned setting the DAQ assitant at 100 samples and 1KHz for the thermocuples. Making an average of the 100 samples for each channel gives a good result from what I have seen in my last test. After this, with another DAQ assistant I am making some other kind of recording at another speed. I know this is not optimized using DAQ Assistant but loss of time and simultanity isn't a problem for me in this project.
However if I had used only one DAQ Assistant for my thermocouples and for the other sensors, a part from the rate vs thermocouples problem, not having the same ranges could have been a problem?
I also don't understand the channel order you mentioned. Still using a DAQ Assistant in what way would this effetc the measures?

Why do TC inputs on my SCB give a 0.0000 output?

I have an SCB-68 connected to a PCI-604E (PCI-MIO-16E-4)DAQ board in my computer with Windows XP. When I open a Test Panel, I can see a reasonable output on channel 0 (CJC) and I can see noise on empty channels, but if I connect a thermocouple to a channel, the output goes to 0.000000. Why?

I'm glad you were able to see a signal in the board's test panel. The way to change the scale on the virtual channel test panel is to change the physical scale in the properties for the virtual channel.
As far as the actual readings go, I've got a couple of thoughts as to why you're not seeing what you expect. First off, the polynomial constants you're getting from the Omega catalog seem to be for a °F scale, but you're specifying the range for the virtual channel in °C. You may have meant to do this, but it's just something to double-check.
Second, I'm a bit confused by the way you're creating the custom scale. The omega equation is a 5th-order polynomial, but when you calculate the reverse coefficients, you specify
a 6th-order equation. This shouldn't be a problem as long as you enter all of the coefficients correctly, but you may want to stick with a 5th-order since that is the original format.
There's one thing you may want to try that (in my opinion) simplifies custom scaling. You can create a table of points using the original 5-th order equation from Omega and input these values directly as a Table Scale in MAX. This avoids some of the hassle of having to reverse-calculate coefficients since the original equation goes from temp. to volts and not vice-versa. This can be done easily in Excel and the calculated points can be saved as a text file. You can then create a Table Scale in MAX that reads directly from that text file. I think it helps to see some representative table values rather than an ambiguous polynomial equation.
These are just some things to consider when you get back to your office. Please let me know if you still can't get the readings you expect.
David
David H.
Systems Engineer
National Instruments

Scb 68 counter

I am using an scb 68 connected to a pci 6221.
I require an application where the 16 analog inputs are used to count events. Every analog input has two values (1 or 0) like TTL signals. The problem is that I am using the vi "elapsed time" to measure the time of the events and the time is not accurate nor constant. I´ve read that counters should be used but that is impossible because the scb 68 only has 2 counters and i require 16.
any suggestion?
i've thought on creating my counters physically and use the result with labview, although the utility of the program and the scb 68 card would be negligible.
Miguel Angel

Miguel,
It is hard to tell from an image, but here are a few things to consider:
1. The DAQ Assistant is not considered to be optimized for high performance. It is set up for ease of use. It is often better to use the low-level DAQ VIs. Do the configuration and initialization outside the loop and clear the task after the loop finishes. Just read the data inside the loop.
2. The filters may take longer than you think. It depends on the complexity of the filter and the amount of data. Is the filter VI reentrant? If not you may have issues with the filter transients. If you have the VI Profiler, use it to see where the timing bottleneck is located.
3. Local variables are slower than wires. I do not see the v1.2, c1.2, ... indicators or controls in the image posted. Setting up a shift register to pass the data from iteration to iteration or an Action Engine to pass data from a parallel loop may be faster.
4. Do you need to update the indicators 20 times per second? The user cannot see update quite that fast and it looks like that data is just incrementing. If you only write to the
indicators 2-3 times per second (or, better, yet, in a parallel loop), this might speed things up a bit. Panel updates require OS action and your program has no control over how the OS handles that.
Lynn

Frequency divide by N doesn't work on Counter-Timer PCI-6602

Hello everybody,
I tried to do something basic ( ?) with this Counter-Timer 6602 Board, and it doesn’t work.
So I hope some people with more experience than me could understand what happens here.
1) What I need:
I need to generate 4 synchonised clocks, whose periods will be multiple of 1 ms.
2) What I have:
LabVIEW 7.0 and a PCI-6602 Counter-Timer Board in a DELL PC running under XP pro.
The PCI-6602 Counter-Timer Board has 8 counter timers named CTR 0, CTR 1, ... CTR7.
3) What I have already done, and that worked:
- Generate a 1 kHz “Master Clock” signal from CTR 4, configured by “Continuous Pulse Generator Config.vi” (found in “Data Acquisition, Counters...).
- configure CTR 0 and CTR 1 to work as frequency dividers, by use of “Down Counter or Divider Config.vi”.
- Apply the output signal of CTR 4 (OUT ) to the SOURCE inputs of CTR 0 and CTR 1 by means of physical wiring in the SCB-68 connection box.
When I do this, I get two nice secondary clock signals on my oscilloscope screen, ( with periods = 3 ms, or 5 ms or whatever multiples of 1 ms I choose) from CTR 0 and CTR 1 outputs , very clean and perfectly in phase with the 1 kHz Master Clock.
So far, so good...
But I still need 2 more secondary clocks...
One would say: “No problem, do the same trick with two other counters...” Well, not so simple, it seems...
4) What I tried to do, and that didn’t work:
When I try to do the same frequency division with any of the remaining counters, (CTR2 to CTR7), the program stops and I get an error “ –10020 : Time base not valid “.
I can’t figure out what happens here: I thought any counter could be configured to work as a frequency divider, but it seems not to be so, and I am stuck here.
Has anyone an idea about how to fix this type of problem?
Attached file: hor_div02New.vi
Attachments:
hor_div02New.vi ‏123 KB

karolik,
I'm just adding a followup in English. As Marc L. mentioned, the particular vi named "Down Counter or Divider Config" isn't compatible with the 6602. While the 6602 does have the ability to generate 4 synchronized clocks, a different syntax is needed. Here's how I'd do it:
Traditional NI-DAQ
1. Configure a continuous pulsetrain on CTR 4. Route its output to, say, RTSI 4. Don't start it yet.
2. Configure CTR 0,1,2,3 for continuous pulsetrains using RTSI 4 as their "timebase source." Start them.
3. Start the CTR 4 pulsetrain.
4. Now CTR's 0-3 should generate separate clocks with synchronized phasing.
DAQmx
1. Configure a continuous pulsetrain on CTR 4. Don't start it yet.
2. Configure CTR 0,1,2,3 for continuous pulsetrains using "Ticks" for units. Use a DAQmx property node (probably Channel property node, but am not 100% sure and don't have a LV PC handy to check) to specify that the "ctr4 internal output" should be used as the timebase. Start them.
3. Start the CTR 4 pulsetrain.
4. Now CTR's 0-3 should generate separate clocks with synchronized phasing.
-Kevin P.

I have a magnetic pick up sensor

I wanted to measure the speed of an engine (flywheel). I have a encoder type sensor with a magnetic strip inside (hall effect type),mounted on the flywheel (with 12 holes). The magnetic pick up sensor, generates a pulse train (Is this a TTL signal?). I wanted to measure the speed of the flywheel, by measuring the frequency/time period/width of the pulse. I have a AT-MIO-16E-10 data card inside my PC and AMUX-64T Multiplexer. Can I use them to measure the speed of the engine. I have a SCB-68 connection box, connected to another PC, which I'm using to measure the in-cylinder pressure (high frequency) triggered with a external scan clock, which has a "Crank angle encoder" as source.(pulse per every 1/2 CA =720 pulses/rev).
Index pulse (D
igital trigger) is connected to PFI0
External Scanclock source is connected to PFI7.
We are using slightly modified "acquire Nscans-external scan clk D.vi" for measuring in-cylinder pressure.
I just wanted an efficient way of measuring the speed of the engine with the equipment I have.

Hi Mr.Filipe A.,
Thanks for your response. We are using labview (version 5.0). I have few more questions.
1) I have a SCB-68, connected to another PC (first PC is connected with AMUX-64T), which I'm using to trigger the in-cylinder pressure (high frequency) with a external scan clock, which has a "Crank angle encoder" as source.(pulse per every 1/2 CA =720 pulses/rev).
Index pulse (Digital trigger for TDC) is connected to PFI0
External Scanclock source is connected to PFI7.
As the encoder and digital trigger are connected to two pins (PFI7 and PFI0 respv.). Will I be able to connect the speed pick-up sensor, also to the same SCB-68, (if so what are the available pins numbers, do I have to use to connect the gate source for my speed pick-up).
2) Can
I use the crankangle encoder only to measure the speed of the engine? if so how?. Im already using the crakangle encoder in "acquireNscans-externalscanclkD.vi.". Can I use it for two different applications?
3) If I have to get another SCB-68, will I be able to connect that in series with AMUX-64T, so that I can get the readings in first PC, only.
Thanks for your time,
Surya.

How do I synchronize a pulse output to a sine wave input on a pci-6602 card?

I have a sine wave from a function generator as the input on the source of a counter. Input frequencies vary from 2-60 kHz. I want to produce a pulse train at a different frequency (10 Hz), but in phase with the sine wave. I have only been using Labview 5.1 for a short time. I am using the PCI-6602 card with a SCB-68 connecting block.

Hello;
Unfortunately, you can't connect a analog sinewave to the counter source. Counters only work with digital TTL signal type. To accomplish that task, you will need a MIO board working in sync with the 6602 you already have.
Regards
Filipe A.
Applications Engineer
National Instruments

Angle Encoder for Position measurement on SC-6281

Hi,
I'm trying to connect a quadrature angle encoder with 3600 ppr to the general purpose counter/timer of a M-Series SC6281 DAQmx board. We use C and have tried using the AngularPosition-Buff.c example code but to no avail. We simply want the counter to tell us the angle of the encoder at any given time....can you help ? We've wired up the encoder correctly (i.e. A connected to PFI 8, B connected to PFI 10 and Z connected to PFI 9) on an SCB-68 connecter block. The C example works as such but it sems to require an extyernal clock sample ? Why is this if we're only counting pulses ?
We also need to determine direction so any help anyone can provide will be gratly appreciated.
Cheers, Shaun.

Just to expand a bit: We have succeeded in generating a continuous pulse train on ctr1 ?(using DigPulseTrain-Cont.c example) and we have been able to feed this into ctr2 and count it (using the BuffSemi-Period-Finite.c example)
We have also managed to feed the pulse train from ctr1 into ctr2 and use it as the sample clock for the AngularPosition-Buff-Cont.c example. The problem is we're getting gobbledygook back as results.
Can anyone help here ?
Here's our resulting code:
Attachments:
DigPulseTrain-Cont.c ‏6 KB

Lego and DAQ

Hello there, I am using a sensor attached to the SCB 68 connecting block of my PCIe 6321 NI X DAQ device.
Is it at all possible to connect lego NXT to the same connecting block so as to use the sensor and lego NXT together in Labview?

Hi Jolanta,
I have created a quick VI that shows that you can read data from a PCI DAQ Card and read data from an NXT sensor within the same VI. Therefore it should be possible to read your sensor data and control your NXT motors.
Please let me know how you get on.
Regards,
Ben B.
Applications Engineer
National Instruments UK & Ireland
"I've looked into the reset button, the science is impossible!"
Attachments:
NXT with DAQ.vi ‏58 KB

1520 shunt cal

Pardon the previous post, it went up prematurely.
I'm using the SCXI 1520/1314 with a quarter-bridge configuration to do a simple strain measurement with shunt calibration. I have a the standard 100K resistor installed at SCA0 and a 11,880ohm resistor installed at SCB0. When I select SCA or SCB and specify the respective installed shunt resistance, I get the error 200007 regarding shunt calibration gain adjust being out of bounds. I can only get the VI to work by selecting SCB and specifying 100Kohm shunt cal resistance (the resistance installed on SCA). With those settings, I obtain a valid gain value (around 1.003) and I can apply known strain to the gage and read reasonable values. The reverse does not work either (using SCA with 11,880ohm specified). I've checked my wiring and all seems to be correct. Is there something wrong with my VI???
Greg R.
Attachments:
strain03.vi ‏27 KB

I have found some answers… and have some more questions.
First, some of my problems with shunt cal were due to poor connections in the 1314. In particular, the SCA/SCB jumper connections are paired up with another wire (here at the QTR terminal, see Fig 2-1 on pg 2-2 of the SCXI 1520 User Manual). As noted in the manual, the method of just putting two wires into the terminal w/o joining them together can produce an unreliable connection. I soldered these wires and presto, the shunt cal began to operate w/o the error mentioned above. Then I had other problems.
Second problem is that it appears the SCA is always assumed in the DAQmx Perform Shunt Calibration (Strain).vi. To show this, I set up SCA(11,880) and SCB(no resistor), selected SCB with a DAQmx Channel property node, and specified the Shunt Resistance to be 11,880 (the resistor on SCA) using the DAQmx Shunt Cal VI. The shunt cal completed without errors, which clearly would not happen if SCB were actually used. So it seems that the AI.Bridge.ShuntCal.Select is never used by the above VI.
Third problem is that after shunt calibration, there is a large bridge offset. After some investigation, I realized that the bridge offset was the same as the shunt cal offset. It appears that the SCA switch is closed during shunt cal, but never opened afterward. I’m going to try to use the AI Parameters.VI to force the SCA to open after calibration, but my lab computer build does not currently include the “Data Acquisition” module. I’ve attached my final VI.
Greg R.
Attachments:
strain05.vi ‏33 KB

SCB 68 connections

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