Application Notes on Restrictors, Pressures, and Flow Recommendations |
Who is the manufacturer of the passive (no electrical power required) flow controller used in the 3000TAXL? (Must be specified as an option.) |
Please recommend a compatible fitting to connect the instrument to 1/4" copper tubing. |
Does the 3000T have internal alarm relays that are able to power up a 24VDC external indicating light? For example, if the concentration goes above certain level, the alarm relays will power up this light. |
How does calibration gas preparation tolerance error affect the accuracy of the analyzer when in service? |
How do you determine the need to replace the micro-fuel cell in Teledyne trace oxygen analyzers? |
We have a cylinder with 8000ppm (0.8%) O2 in N2 span gas. we need to do a remote span cal via valve box from our computer.
How do I enter span value (8000ppm) into the 3000TA-XL analyzer, or has it been set as the default value? When i tried to do manual span and pushed the span button on the front panel of the analyzer, it indicated that it can be done only in remote mode. If I can't enter the span value from the front panel, how i can enter it in remote mode? |
When we send span command from our PLC to the Valve box and the valve box opens high cal gas valve and sends span command to analyzer, and analyzer starts spanning, how we will know that span cal has been done and what time it needs to do span? If we can't enter span hold time (the time between high cal gas valve opening and the start of span cal), how we can be sure that span cal has been done properly? The analyzer needs some time to be purged by span gas before cal start as well. |
Why are "span and zero cal gas press lo" LEDs are always on, while we've connected cylinder with span gas with 150 barg pressure, and we've set 0,5 barg pressure after our GO pressure regulator? We have pressure in the span line, but span low pressure LED is always on. Also we use low cal gas valve for purging sensor with UHP N2, and "zero gas press lo" LED is also always ON, but we have pressure in the zero gas line. |
What events will trigger the system alarm? |
When I use the remote cal inputs, does the unit perform a normal calibration, wait for the slope to be close to minimum and than accept the value and/or can I also define a minimum time for the calibration interval?
|
For additional questions, please contact Technical Support.
Q: Application Notes on Restrictors, Pressures, and Flow Recommendations
A: Please find the Application Notes here.
Back to Top
Q: Who is the manufacturer of the passive (no electrical power required) flow controller used in the 3000TAXL? (Must be specified as an option.)
A: VICI Metronics Inc. Condyne Div., FC30AS4K with stainless steel fittings 6-0016-0
Back to Top
Q: Please recommend a compatible fitting to connect the instrument to 1/4" copper tubing.
A: Swagelok sells VCR quarter inch compression fitting adapters. The ordering number for this 1/4" VCR to 1/4" tube connector is SS-4-WVCR-6-400. You will also need gasket P/N NI-4-VCR-2-GR-VS.
Back to Top
Q: Does the 3000T have internal alarm relays that are able to power up a 24VDC external indicating light? For example, if the concentration goes above certain level, the alarm relays will power up this light.
A: The alarm relays in the unit are dry contacts. They have no voltage themselves to drive a light. Customer would need to supply a light and a voltage source and connect to the alarm relay.
Back to Top
Q: How does calibration gas preparation tolerance error affect the accuracy of the analyzer when in service?
A: To calculate this we first can model the output of the ufuel sensor as linear:
I.e. the current the sensor produces (expressed in Ameres, A), if a linear function of the O2 concentration:
mathematically:
I = O2 * m, where m is the slope coefficient with the units of (A/ppm O2)
(more rigorously, the sensor also has a small offset which is neglected in this discussion)
Then, we can develop in a closed form equation the relationship between measurement inaccuracy and error in calibration cylinder analysis:
First we can state that:
O2 calculated = (slope determined at the time of calibration) * I
O2 actual: (actual slope) * I
Slope calculated at the time of calibration = (calibration gas cylinder analysis value) / Calibration Current
Actual Slope = (real gas concentration) / cal concentration
Therefore the measurement error = O2 calculated - O2 actual
= I * ((calibration gas cylinder value) / calibration current) - (actual calibration cylinder value / calibration current)
So as one can see from this equation, as the measured current gets smaller the error approaches zero.
If one is interested plugged real numbers into the equation, we can say that the normal sensor slope is approximately 3nA/ppm O2.
So if we had a 8ppm cylinder analyzed to 8.2ppm, the error at 1ppm would be:
=3 * ((8.2)/24 - (8/24)) = .025ppm
The sketch below shows the graphical relationship:
Back to Top
Q: How do you determine the need to replace the micro-fuel cell in Teledyne trace oxygen analyzers?
A: Please refer to this document:
MFC_End_of_Life_Determination.doc
Back to Top
Q: We have a cylinder with 8000ppm (0.8%) O2 in N2 span gas. we need to do a remote span cal via valve box from our computer.
How do I enter span value (8000ppm) into the 3000TA-XL analyzer, or has it been set as the default value? When i tried to do manual span and pushed the span button on the front panel of the analyzer, it indicated that it can be done only in remote mode. If I can't enter the span value from the front panel, how i can enter it in remote mode?
A: The span value must be entered manually at the front panel by entering the span mode pressing the span key. So it would be a good idea to set the Valve Box to Local mode and then do a manual span through the front panel of the 3000TA-XL. You will find a screen, that will let you adjust the span value.
Thereafter, every time you do a span command through the valve box, the analyzer will automatically span to the value you set. Even if you power down, the analyzer will remember the value.
Back to Top
Q: When we send span command from our PLC to the Valve box and the valve box opens high cal gas valve and sends span command to analyzer, and analyzer starts spanning, how we will know that span cal has been done and what time it needs to do span? If we can't enter span hold time (the time between high cal gas valve opening and the start of span cal), how we can be sure that span cal has been done properly? The analyzer needs some time to be purged by span gas before cal start as well.
A: To do this use the profibus data coming out of the valve box. In particular, you need to check the fourth least significant bit of address #30. This bit monitors feedback from the analyzer, it is TRUE when the analyzer is either spanning or zeroing, and it is FALSE when the analyzer is back in Analyze mode. Check table 3-6 on the valve box manual to see what information is available as feedback to you besides this.
Back to Top
Q: Why are "span and zero cal gas press lo" LEDs are always on, while we've connected cylinder with span gas with 150 barg pressure, and we've set 0,5 barg pressure after our GO pressure regulator? We have pressure in the span line, but span low pressure LED is always on. Also we use low cal gas valve for purging sensor with UHP N2, and "zero gas press lo" LED is also always ON, but we have pressure in the zero gas line.
A: This feature is for regulators that have pressure switches included to be used as signals when the cylinders are low. If you have them, you need to wire them to the input terminals on the back of the valve box. They should be the type that close when the pressure on the cylinder is low.
If your regulators don’t have this pressure switches, place a jumper across the terminals inputs on the back of the valve box. One jumper for the span lo terminals and one for the zero lo press terminals. The short will turn the lights off.
Back to Top
Q: What events will trigger the system alarm?
A: The system alarm will be triggered by:
Loss of power
Internal power supplies deviate from specification
Failure to span, because output of sensor is too small (less than 0.95 na/ppm )
Failure to zero, because cell offset on zero gas was too high (> 11 nano amp current detected approximately)
Failure during self diagnostic, either by command or at power up. Self diagnostic checks: (1) if power supply voltages are out of specification, (2) if amplifier does not pass simulated input, and (3) if DAC does not have expected output.
Back to Top
Q: When I use the remote cal inputs, does the unit perform a normal calibration, wait for the slope to be close to minimum and than accept the value and/or can I also define a minimum time for the calibration interval?
A: When a remote calibration is initiated, the analyzer performs a calibration the same as a calibration done manually in AUTO mode. The analyzer will wait for the slope to become small and then start the timer. With standard 3000T-XL software, the option to set the timer is in minutes specifically for the span calibration. In the case of the zero, it is hard-coded in the software at approximately 5 minutes. In the case of "Linde" version of the software, the zero as well as the span calibration has a timer, settable up to 5 minutes.
Back to Top
