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LED Output
Shay
Member
05-04-2006 06:10 AM
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Hi there all,
I have a thermocoupe connected to a NI USB-6009 DAQ.
I want to switch 2 external (on the digital I/O side of the DAQ 0-5V)
LEDS on/off dependant on the voltage level of the thermocouole input.
How do I do this... I have a little tester running but I'm not to sure
how to assositae a switch for example to one of the external LED's.
Thanks loads,
Shay
I have a thermocoupe connected to a NI USB-6009 DAQ.
I want to switch 2 external (on the digital I/O side of the DAQ 0-5V)
LEDS on/off dependant on the voltage level of the thermocouole input.
How do I do this... I have a little tester running but I'm not to sure
how to assositae a switch for example to one of the external LED's.
Thanks loads,
Shay
Dennis_Knutson
Knight of NI
05-04-2006 09:38 AM
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What do you mean by "assositae a switch"? By your description, you would have some comparison done on the analog input and based on that, set a Boolean value that you would pass to a DAQmx Write set to digital output. The setting of the digital output could be done in something as a case statement. What are the conditions that you want to test for and the corresponding digital outputs?
Otis
NI Employee (retired)
05-05-2006 02:45 PM
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Hi Shay,
First off, I wanted to let you know that trying to read a thermocouple with a USB-6009 is not the most accurate system in the world.
The USB-6009 has 14-bit resolution with a minimum range of +/- 1 volt. This gives a voltage resolution of 122 microvolts. The estimate of the response of different thermocouple types can be seen below.
Common thermocouple types have the following response:
K type: 41 microVolts per degree Celsius
J type: 56 microVolts per degree Celsius
T type: 52 microVolts per degree Celsius
Essentially that means that if you are using a K Type thermocouple then you are only going to notice a change of temperature for every 3 Degrees C (~5.5 Degrees F). This might work for your application, but just keep in mind that you have pretty poor resolution when trying to read a thermocouple with a USB-6009.
Other than that, for the switch you can't source much amperage from the USB device, but other than that, just do a digital output and it should work fine.
First off, I wanted to let you know that trying to read a thermocouple with a USB-6009 is not the most accurate system in the world.
The USB-6009 has 14-bit resolution with a minimum range of +/- 1 volt. This gives a voltage resolution of 122 microvolts. The estimate of the response of different thermocouple types can be seen below.
Common thermocouple types have the following response:
K type: 41 microVolts per degree Celsius
J type: 56 microVolts per degree Celsius
T type: 52 microVolts per degree Celsius
Essentially that means that if you are using a K Type thermocouple then you are only going to notice a change of temperature for every 3 Degrees C (~5.5 Degrees F). This might work for your application, but just keep in mind that you have pretty poor resolution when trying to read a thermocouple with a USB-6009.
Other than that, for the switch you can't source much amperage from the USB device, but other than that, just do a digital output and it should work fine.
