Thermocouple signal input range question

So i searched far and wide to find an answer to this, and figured somebody on here would have the answer. Id like to know if setting a smaller signal input range(closer to what temps we are testing at) such as 0-200f then just a covering the complete thermcouple range say -100f to 600f is benefiicial. In other words does this narrow range allow the unit to work more accurately because it only has to "search" through a smaller temp range, compared to a larger range.
Thanks

What hardware are you using to measure the temperature and how are you measuring in your program?
I always choose a range to measure instead of the full range of the TC, it just makes me feel better.
The multifunction DAQ cards will switch gains depending on the min/max voltage that you are reading. I am guessing that if you set up a TC channel in MAX it would automatically switch to the highest gains because it would know that TC readings are low voltage.
Dedicated TC modules like the ones that the cDAQ uses do not have multiple gain settings. Basically because it is set up to only read TC's and not higher voltages.
So then it would come down to if you have 16-bit, 18-bit or 24-bit resolution on the measurement hardware for actual accuracy.
I am sure someone will correct me if I am wrong.

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In Labview 8.5, what happens if the signal input exceeds the signal input range set by the DAQ Assistant?

Hello all,
This should be a pretty simple question, but I can't seem to find the answer on-line and don't currently have the capabilities to test this:
I'm using LabVIEW 8.5 and have a VI that imports sensor data through the DAQ Assistant. In the configuration tab there is a signal input range. What happens if my sensor exceeds this range? Will I get a warning? Will the value default to the maximum (or minimum)? I was interested in writing in some code to display an error as I approach the limits of this range, but was unsure if I also needed to include some code to display an error if the range is exceeded as well.
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Tristan
Solved!
Go to Solution.

Hello Tristan,
The behavior depends on the range you choose and the device you are using.
If you are using a device with only one valid input range, we will use this range even if you set a smaller minimum and maximum in the DAQ Assistant. Thus, if your device only supports ±10V and you set the range to ±8V, you will still continue to get valid data after your sensor exceeds 8V until you approach 10V. Once you reach the limit of the range of your device, the output will "rail" and just return the maximum value until the signal drops below the maximum again.
Note: A device that is nominally ±10V usually has some overshoot (like ±10.2V) that is typically specced in the manual.
However, if you are using a device with multiple input ranges then things get more complex.
The NI-DAQmx drive will pick the smallest range that fully encompasses the range you choose. So, suppose your device supports the following input ranges: ±0.2V, ±1, ±5V, and ±10V and you choose 0V - 3V as the range in the DAQ assistant. The NI-DAQmx driver is going to look at your input range and the list of input ranges that your hardware supports and choose the smallest that encompasses the full range you set. This would the ±5V, because that's the only range that contains up to 3V. As a result, any input signal between ±5V will be returned and any outside this range will "rail" to either the maximum or minimum value.
We do this because using smaller ranges make more effective use of the resolution of the ADC. Thus we try to use the most efficient range based on what you request without picking a range that will cause you to miss data.
Let me know if I can clarify this further.
Seth B.
Staff Test Engineer | National Instruments
Certified LabVIEW Developer
Certified TestStand Developer
“Engineers like to solve problems. If there are no problems handily available, they will create their own problems.”- Scott Adams

Is there a way to get more voltage input range from an SCXI-1520?

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I will not answer your question but will ask you something that may be familiar to you.
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HT201700 Voltage input range for original Macbook air 2008/2009

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Can I set different input range in different channel in cFP AI100

Dear Sir:
I have one question about the input range of cFP AI 100. Can I set different input range for different channel in one cFP? Also, can I set different input type (voltage or current) for different channel in one cFP? If yes, how? Thanks.
Best Regards.
Fred

Hi Fred,
The answer to both questions is yes. In MAX, in the Channel Configuration Tab of your cFP-AI-100, you can specify your range to be one of a number of settings for current or voltage. To configure separate channels, simply select the channel and then select the range. See the attached screenshot for more details.
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Attachments:
FP Channel Configuration.bmp ‏2305 KB

How can I change Fieldpoint input ranges programatically?

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Has anybody done this before for any modules and can give me some hints
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Rainer,
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PID VI - Output Range Question

I have a question concerning the PID VI and it's output range option.
"What is gained or lost from using 0-100 versus -100 to 100 for a default output range?"
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My application provides the PID VI a setpoint and a process variable, both in degrees Celsius. I see that the output from the VI has a default range of -100 to 100. The power supply that I want to power accepts an input range of 0.0035 - 0.020 mV.
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I can get other values if I use the larger scale and then convert them to the smaller numbers. I am trying to decide between using the range 0 - 100 or going with the default range of -100 to 100 and simply cutting off anything below zero in the conversion to mV. What is gained or lost from using 0-100 versus -100 to 100 for a default output range?
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Attachments:
PID Single.vi ‏129 KB

Not receiving any signal input with LabVIEW SE, USB DAQ board

Hello all, good afternoon.
I am having a little trouble with my DAQ device, I hope that someone will be able to help me.
I'm plugging a BNC pH sensor to a NI USB 6251 M-series board, to try and obtain the electrical response of that particular sensor, measuring the voltage output for each buffer solution (pH 4 and 7). Have 9.2.3 mx (lastest) drivers.
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If I plug a voltimeter to the wires that are going into the analog inputs (after conditioning), it measures about 50 mV, which is a lot more than the 1 mV the board is measuring, but a lot less than the ~180 mV I should be measuring with a pH 4 buffer solution.
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I think it might have to do with the signal conditioning I'm doing, or some sort of configuration with the hardware of the DAQ board.
So, any idea what I might be missing?
I'm a week behind schedule because of this, hopefully I will find my answer here.
Thank you very much in advance!

Good afternoon.
Yes I have tried all of that. The board responds very well when a flat 5V DC voltage is fed into a channel.
However after much investigation I believe to have found the problem yesterday, it probably has to do with the operational amplifiers I was using. The input bias current was in the magnitude of nanoAmps, while for pH measurements an IBC of picoAmps or less is necessary due to the high impedance of the sensor. This was causing a drift of over 100 mV on my output which is about 2 pH and thus unnacceptable (even though I had the Bias resistors at the input to ground, like suggested in the NI tutorials, but apparently they were not enough to compensate for the high IBC).
In the lab all available op-amps suffer from this, even Instrumentation op-amps like AMP04 from Analog Devices. I still haven't had a chance to acquire new op-amps with the necessary IBC but hopefully it will do the trick. Makes sense since I checked the datasheets for every op-amp in the lab, and they all had IBC around 400 nanoAmps (and none of them worked), while every single op-amp for every pH meter circuit I found have IBC's of pico/femtoAmps.
The sensor I'm using is from AquaMedic, I'm not sure what the model is, but it's a cheap plastic sensor that comes bundled with their pH Computers.
Thank you very much for your input.

How to modify input range (DAQ assistant) with a numeric control ?

hello every one
I am currently working with the NI USB-6218 acquisition card.
I would like, in order to acquire a signal, to be able to choose the input range of the DAQ assistant with a numeric control ( and not by opening the DAQ assistant window ) (like the "number of sample" and the "rate" entry...)
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Thanks so much in advance for your answers !
Solved!
Go to Solution.

hello
sorry I forgot it. but after spending a few hours on the problem this morning, i solved it Apparently, I corrupted the general DAQmx assistant last friday. By restarting my computer this morning, this issue was solved and I was able to transform the constant into command for the input range.
Thanks a lot for your help !!!
Guyua

Can input range limit be modified while AI Read running

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Configure the acquisition to sample the same channel multiple times, each at a different gain. Use a short (10 or 100 usec ?) interchannel delay so these samples are taken close together in time to each other. Then in software examine the data from all the gain setting to determine the highest gain that did not saturate. If the gains are well matched (a signal of 0.5 V gives the same data value on a 1V input range as on a 10 V range), then the values can be combined into one final data array. If not, then keep a running separate array for each gain and only use the array from the gain which did not saturate over all data values.

NI 9223 - current input range

Hi,
The datasheet at http://sine.ni.com/ds/app/doc/p/id/ds-260/lang/en just talks about the range of voltage to the analog input. I don't see any places else having the information on the limit on current. I would assume that we have a current range for these analog inputs. Could anyone give the document for this?
Thanks
Solved!
Go to Solution.

The input in question is a true voltage input. Its input resistance is very high and can be supposed to be infinite for most calculations.
So it does not really have a maximum input current. Of course it might be possible to destroy the input circuitry by overcurrent. Also you cannot force more current into an analog input than it actually consumes. The so-called bias current, as mentioned, is in the pA range.
Even if you make the input a part of a circuit with usually high current (let' s say 1 A), the current in a closed loop is always determined by the component with the highest resistance/impedance. Again, since the input resistance is very high, the current in such a circuit would be limited to the input current mentioned. (This is rather theoretical but with an ideal current source the input voltage might exceed the limits. A photomultiplier is close to a ideal current source and the voltage across the input might raise higher than the voltage limit given.)

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About a year ago my 4 yr emac that I gave my dad starting having the video on the built in display go out periodically. When it started happening more and more, rather than get a whole new computer, we purchased a 22 widescreen VGA monitor and hooked it up via a mini-DVI to VGA adapter. Everything was great and worked perfect. Just last week all of a sudden the VGA monitor is displaying "No Signal Input" The emac is starting up and making all of the correct sounds, but no picture at all.
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The next thing I was going to try was to reset the Parameter RAM.
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What are the odds that the Mini-DVI to VGA adapter just went bad?
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HOW TO set the input range for analog in (DAQ)?

How can I set the input range of a - NI DAQ USB 6259 - analog voltage input?
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duplicate post

Monitor display no signal input

my computer turn on but the monitor display no signal input. I plug my monitor to other computer and the screen shows my icons and everything but when I plug other monitor to my computer it say no signal input. How do I fix my computer to communicate with the monitor.

When desktop goes blank then there's no more signal from the pc.
So the monitor says 'NO SIGNAL INPUT'.
What's the problem?
V.
*** Say 'Thanks' with Kudos ***

Input range for different channels

Hi,
In one of my experiments, the data I acquire in different channels have different magnitudes (in Volts). Therefore, I am trying to set a different input range to these various channels. Here's a picture (input_range.png) of a part of my VI where I am trying to assign input ranges to the analog input channels.
Channels ai0-7 have the range +/-200mV and channels ai8-15 have +/-500V. I do not have the equipment with me at the moment, so I can't test this. But I am wondering whether this is how you would normally set different input ranges for different channels or whether there's a better way to do this.
Cheers.
Attachments:
input_range.PNG ‏15 KB

Thanks for the quick reply Mike.
I found the following post which showed me how to do it
http://forums.ni.com/ni/board/message?board.id=170&message.id=318492&query.id=74076#M318492
However, I am having difficulties in actually acheiving this. Firstly, I don't know how to set up the arrays as he's done there. Secondly, I could not get the auto-indexing to work. I've attached a pic of my attempt. When I try to enable auto-indexing on the right-hand side of the for-loop it breaks the wires and I can't even enable auto-indexing on the left hand side.
Will it be possible to attach a VI for this part so I can see what functions you've used.
Cheers.
Attachments:
input_range2.png ‏8 KB

Thermocouple signal input range question

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