Frequently Asked Questions

3000 Series Application Notes on Restrictors, Pressures and Flow Recommendations

​​3000 series analyzers require reasonably regulated sample pressures. While the 3000 analyzers are not sensitive to variations of incoming pressure (provided they are properly vented to atmospheric pressure) the pressure must be maintained as to provide a useable flow rate trough the analyzer. Any line attached to sample vent should be 1/4 or larger in diameter. 

FLOW RATE RECOMMENDATIONS: 

A usable flow rate for a 3000 series analyzer is one which can be measured on the flowmeter. This is basically .2 - 2.4 SLPM . The optimum flow rate is 1 SLPM (mid scale). Note: response time is dependent on flow rate, a low flow rate will result in slow response to O2 changes in the sample stream. The span flow rate should be the approximately same as the sample flow rate. 

CELL PRESSURE CONCERNS: 

The sensors used in 3000 series analyzers are optimized to function at atmospheric pressure. At pressures other than atmospheric the diffusion rate of O2 will be different than optimum value. Higher pressures will produce faster O2 diffusion rates resulting in higher O2 reading and shorter cell life. To use a 3000 series analyzer at a cell pressure other than atmospheric, the analyzer must be calibrated with a known calibration gas at the new cell pressure to adjust for the different diffusion rate. Cell pressures below 2/3 atmospheric are not recommended because as they tend to cause excessive internal expansion which may result in seal failure. 

For operation at cell pressures other than atmospheric care must be taken not to change the sample pressure rapidly or cell damage may occur. For cell pressures above atmospheric, caution must be exercised to avoid over pressuring the cell holder. ( percent analyzers will require some type of cell retainer to prevent the cell from being pushed out by the pressure .) For operation at pressures below atmospheric pressure a suffix C ( clamped) cell is required. 

RESTRICTION DEVICES: 

For proper operation, all 3000 series analyzers require a flow restriction device. This device is typically a restrictor or a valve. This restriction device serves two functions in the sample path. The first function is to limit the flow rate of the sample through the analyzer. A restrictor is chosen to operate over a range of pressures and provide a useable flow rate over that range.

The second function that the restriction device provides is a pressure drop. This device is selected to provide the only significant pressure drop in the sample path. 

RESTRICTOR KIT 

The current revision of the 3000 series analyzers are supplied with a kit containing two restrictors and a union which are user installed. These parts supplied to give the end user more flexibility when installing the analyzer. The restrictor kit is suitable for high and low positive pressure applications as well as vacuum service ( atmospheric pressure sample) applications ( see manual for installation instructions).

The standard restrictor ( BLUE DOT ) is recommended for pressures between 5 PSIG and 50 PSIG. For positive low pressure application ( 5 psig or less ) the un-marked restrictor is better suited . For none pressurized sample applications the marked restrictor should be used and configured for vacuum service. Note: for extremely low positive pressure applications ( less then 2 psig) the vacuum service configuration should provide higher performance ( higher flow rates). For vacuum service the end user must supply a vacuum pump and a by-pass valve for the pump. A vacuum level of 5 - 10 inches of mercury should provide the optimum flow rate.

CAUTION: flow restrictors have very small orifices and may be plugged by small particles ( .005” dia or larger) A sample filter must be included in the sample line prior to the restrictor! ( a 60 micron filter is recommended) 

3000TA EXAMPLES:

Example 1

with a incoming pressure of 10 psig the std restrictor (blue dot) will provide a flow rate of .76 SLPM. Up-stream of the restrictor the sample line pressure will be 10 psig, while down stream ( including the cell) the pressure will be at atmospheric pressure.( analyzer vented to atmospheric pressure) Note, all other pressure drops in the sample path are insignificant at these flow rates. This insures that the cell operates at atmospheric pressure. At very high flow rates ( off scale of flow-meter), pressure drops other than the restriction device could become significant , and result in pressurizing the cell. 

Example 2

A 3000TA is configured for vacuum service as follows. The un-marked restrictor is placed in the sample vent port. The down stream end of the restrictor is then connected to a vacuum pump and by-pass valve. The by-pass valve is adjusted to provide a flow rate of 1 SLPM. The sample pressure between the pump and the restrictor will be approximately -7 inches of mercury, while the pressure in the balance of the sample system including the cell will be approximately​ at atmospheric pressure (provided the sample flow into the analyzer is not blocked.) 

BY-PASS: 

To improve the system response, a by-pass can be added to increase the sample flow rate to the analyzer by a factor of ten. A by-pass provides a sample flow path around the analyzer of 2 - 18 SCFH. typically.

CALIBRATION GAS: 

3000 series analyzer requirements for units with Auto-Cal options. The customer must supply a control valves (or restrictors) for any SPAN or ZERO gas source which is attached to the Auto-Cal ports. The valve should be adjusted to the same flow rate as the sample gas . When restrictors are used, the gas pressure must be adjusted to achieve the proper flow rate. 

OPERATION WITHOUT A RESTRICTOR DEVICE: 

Operation without a restrictor device is not recommend as mentioned above. A 3000TA without any flow restrictor device was tested on 11-19-97. This results in a flow rate of 2.4 SLPM @ 1 PSIG. This is a cv of 0.023 for the standard sample system.

TAI PART NUMBERS

RESTRICTOR KIT: A68729 

UNION (SS) U11 

LP. RESTRICTOR R2323( LOW PRESSURE / VAC. SERVICE )

STD.. RESTRICTOR R2324 BLUE DOT 

NUT N73 

FERRULE F73 

FERRULE F74 BOTH FERRULES ARE REQUIRED 

CONVERSIONS: 

1 PSI = 2.04 INCHES OF MERCURY (in. Hg.) 

1 SCFH = 0.476 SLPM

A: VICI Metronics Inc. Condyne Div., FC30AS4K with stainless steel fittings 6-0016-0​

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.​

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.​

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 

A: Please refer to this document:

MFC_End_of_Life_Dete​rmination.doc​

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.​

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.​

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. ​

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.​

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.