OFS-2000 FREQUENTLY ASKED QUESTIONS (FAQ)
--- for your convenience we have compiled a list of answers to questions commonly asked by our customers. If you do not find an answer to your specific query please contact our sales staff by clicking here.
Application/Specifications
1. Describe the major elements of your system.
2. What is the weight of the devices mounted to the port?
3. What are the dimensions of the enclosures used on the stack?
4. What are the dimensions of the enclosures used in the CEM building?
5. Does the Control Box fit a 19-inch rack?
6. Do I need to buy a remote display device?
7. Is optical head purge air required?
8. What are the power requirements of the flow meter?
9. What ambient temperature range is acceptable for stack-mounted electronics?
10. What is the typical required vertical offset or path angle?
11. Are options available for corrosive environment?
12. Are options available for high temperatures?
13. How is your product affected by moderate vibration?
14. What is the minimum port diameter?
15. What is the maximum path length?
16. What is the maximum stack temperature?
17. What cabling is required between the stack instruments and the CEM building?
18. Is there a fiber optic option?
19. What is the maximum distance between the optical heads and the Control Box?
20. What is the maximum distance between the Control Box and the user data acquisition system?
21. What steps are taken to insure lightning suppression?
22. Can setup be completed from the remote display or is any data entered on the stack?
23. What electronics are required on the stack?
24. Is stack temperature measured or calculated from sound speed?
25. In what country is this product manufactured?
26. Does the flow sensor carry the CE Mark?
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Operation
1. How is volumetric flow data corrected for standard temperature and pressure?
2. How are zero and span simulated?
3. How is zero/span check initiated?
4. Is the configuration user friendly and menu driven?
5. Does the remote display give indications of transmitted or received signal strength or signal quality?
6. Can a serial device read results from the flow meter instead of an analog output?
7. How is the flow meter data corrected to agree with the reference system data?
8. For installations that meet the siting criteria, what accuracy and repeatability is expected?
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Maintenance
1. What disassembly is required to clean optical heads?
2. How often should optical heads be cleaned?
3. What indications does the instrument give that the optical heads are dirty or ports blocked?
4. Do any parts require factory calibration to match sensors?
5. Are there any parts that cannot be replaced or calibrated in the field?
6. Are replacement parts interchangeable with each other or are devices factory matched?
7. Is a computer required for setup, troubleshooting, or maintenance?
8. What test equipment is needed to setup, maintain, troubleshoot and repair your system?
9. What is the mean time before failure of optical heads, sensors, amplifiers, and remote displays?
10. How long will you guarantee the availability of spare parts?
11. Can additional troubleshooting data be accessed with a computer from a serial port?
12. Is there a way to visually display the signals from the optical heads for troubleshooting?
13. What routine maintenance is recommended?
14. Are there any maintenance activities that might take more one person to complete?
15. Can configuration parameters be stored electronically and reloaded in the flow meter?
16. Are parts kept in stock?
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Acquisition Factors:
1. What parts and services are not included with the OFS?
2. What system warranty is available?
3. Are computer interface cables included in the quote?
4. Are purge air blowers, filters, and purge air ducting included in quote?
Consumable Spare Parts
1. List the prices of those parts that should be replaced on a periodic basis.
Recommended Spare Parts
1. What parts should be kept in stock to ensure monitor availability?
2. What is the typical price to replace or rebuild optical heads or sensors?
3. What parts warranty is available?
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Application/Specifications
1. Describe the major elements of your system.
The OFS-2000 consists of three major elements. The optical heads are a pair of optical transmitters and receivers referred to as the TX Unit and RX Unit, respectively. A Control Box that connects to the RX Unit houses the digital signal processor and digital display. The Control Box may be either installed on the stack with the optical heads remote up to 300 ft. away in a CEM Building or at the base of the stack. The Control Box has a variety of options to transmit data to the user data acquisition system including 4-20 ma, RS-232, and fiber optic modems.
2. What is the weight of the devices mounted to the port?
Dimensions TX & RX Optical Units 32 x 15 x 15 cm ea (13 x 6 x 6 in)
Weight TX & RX Optical Units 7 kg ea (15 lb)
3. What are the dimensions of the enclosures used on the stack?
Dimensions Control Box 40 x 30 x 25 cm (16 x 16 x 10 in)
Weight Control Box 7 kg (15 lb)
4. What are the dimensions of the enclosures used in the CEM building?
No equipment is necessary in the CEM building if the optical heads and Control Box are collocated on the stack.
5. Does the Control Box fit a 19-inch rack?
The NEMA-4 Control Box is an option. The 19-inch rack configuration comes standard with the OFS.
6. Do I need to buy a remote display device?
No, the Control Box contains an integral digital display and keypad for viewing the data and making all set-up configurations. If the customer does not have a data acquisition system, a personal computer may be used.
7. Is optical head purge air required?
Purge air is not required for the operation of the OFS.
8. What are the power requirements of the flow meter? How many separate circuits are necessary?
a. On stack:
Two circuits are required, one at the TX Unit and one at the Control Box.
TX Unit 100-240 VAC, 50/60 Hz, 12 VA
Control Box 100-240 VAC, 50/60 Hz, 40 VA
b. CEM building:
None if the Control Box is located with stack optical heads.
9. What ambient temperature range is acceptable for stack-mounted electronics?
The OFS system has been tested from 40 to 60 C (-40 to 140 F).
10. What is the typical required vertical offset or path angle?
Unlike competitors, the OFS does not require vertical offsets or path angles. The OFS mounts at the same vertical level at opposing ports.
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11. Are options available for corrosive environment?
Quartz windows are standard on all OFS to combat chemicals or high temperatures. The TX/RX Units are made from Ό inch thick aluminum plate and are protected with powder coat to resist corrosion. The Control Box is housed in a polycarbonate enclosure. All OFS enclosures are rated at IP65 (NEMA 4).
12. Are options available for high temperatures?
Because no other components of the OFS must be located within the harsh stack environment, the OFS performance is independent of stack temperature. A high temperature gasket is used to help isolate the TX/RX Units from the stack skin temperature. The light beam passes through a high temperature window made from quartz. For extremely high temperatures, a gate valve is available for each optical head.
13. How is your product affected by moderate vibration?
The optical assemblies of the TX/RX Units are mounted on special supports to reduce vibration effects.
14. What is the minimum port diameter?
The OFS uses an industry standard 4-inch pipe STD Schedule 40 flange (9 O.D., 7.5 bolt circle, holes at 12,3,6, and 9 o clock positions).
15. What is the maximum path length?
The maximum path length is 10 meters (33 feet). Longer path lengths are optionally available up to 100 m (330 ft).
16. What is the maximum stack temperature?
Because the OFS optical heads do not reside within the stack, the maximum temperature of the stack is irrelevant. The combination of the flange extension and high temperature gasket further isolates the OFS electronics in the TX/RX Units from the internal stack temperatures.
17. What cabling is required between the stack instruments and the CEM building? Twisted pair, coax, multiconductor, fiber?
The standard OFS cable is 10 conductor, shielded (20-22 AGW).
18. Is there a fiber optic option?
Yes, a Fiber Optic Modem (FOM) option is available for installations where the Control Box must be connected via a fiber to the users computer or data acquisition system. The FOM converts the RS-232 levels to light pulses for noise free, long distance transmission. Using two multi-mode fibers (62.5/125), the FOM will transmit over 1 mile at 28.8 kbps. FOMs are used in pairs, one installed in the Control Box and one at the remote computer. The FOM at the user computer converts the light signals back into RS- 232. The user must supply dual multi-mode 62.5/125 fibers with ST type connectors to connect the FOMs.
19. What is the maximum distance between the optical heads and the Control Box?
The maximum distance between the RX Unit and the Control Box is 94 m (300 ft) using the optionally supplied cable. The standard cable supplied with the OFS is 5 m (15 ft).
20. What is the maximum distance between the Control Box and the user data acquisition system?
The maximum distance between the Control Box and the user computer or data acquisition system depends on the Control Box communication option. Cables between the Control Box and the user equipment are not supplied with the OFS. - RS-232 15 m (50 ft)
- RS-422 1200 m (4000 ft)
- RS-485 1200 m (4000 ft)
- Limited Distance Modem 4.8 km (3 mi) on 24 AWG wire pairs
- Fiber Optic Modem 1.6 km (1 mi) on two multi-mode fibers (62.5/125)
- 4-20 ma Loop Up to 600 ohms loop resistance (length depends on wire gage)
[return to top] 21. What steps are taken to insure lightning suppression?
All power and signal input/output lines are protected against spikes and surges. This is a standard feature on all OSi products.
22. Can setup be completed from the remote display or is any data entered on the stack?
Set-up data can be entered either at the Control Box using the integral keypad & display, at the Control Box using a laptop computer, or over a serial data line at the customer data acquisition system.
23. What electronics are required on the stack?
The TX and RX Units (optical heads) are always installed on the stack. The Control Box may be installed anywhere within 94 m (300 ft) of the RX Unit using optionally available cable. OSi prefers collocation to minimize possible electrical noise and signal degradation that can occur to long cable lengths.
Collocation also allows one person to perform maintenance activities since all equipment is at the same spot.
24. Is stack temperature measured or calculated from sound speed?
No, stack temperature is neither measured nor required for optical velocity measurements. The OFS velocity measurement using optical technology is independent of stack temperature and pressure.
25. In what country is this product manufactured?
The OFS-2000 is manufactured at the Optical Scientific, Inc factory in Gaithersburg, Maryland USA.. OSi is an ISO-9001 registered company.
26. Does the flow sensor carry the CE Mark?
Yes, the OFS-2000 has been tested for UL, CSA, and CE Mark requirements. The following certifications have been obtained: - UL 3101-1:1993
- CSA C22.2 No. 1010.1:92
- IEC 61010:1999
- UL 3101-1:1993
- CSA C22.2 No 1010.1:92
- IEC 61010:1999
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Operation
1. How is volumetric flow data corrected for standard temperature and pressure?
The OFS measures the velocity of the stack gas. This measurement is independent of temperature and pressure. The user data acquisition system can be programmed to convert the OFS velocity into standard scfm by inputting the stack diameter, pressure, and temperature.
2. How are zero and span simulated?
During the auto-calibration cycle, the OFS injects precise phase shifted frequency pairs that represent ~10% and 60% of full scale. The calibration frequencies are injected one at a time and the resultant velocity is shown on the Control Box digital display. If one or both of the calibration values are outside the range of +/- 3% of the standard value, the calibration is registered as a failure. The total autocalibration time depends on user settings (2-18 minutes).
3. How is zero/span check initiated?
The OFS is equipped with a calibration system that operates once per day automatically. It may also be activated by sending an ASCII R character over the serial interface, by following the steps in the OFS set-up using the keypad and display, or by cycling the AC power to the OFS Control Box.
4. Is the configuration user friendly and menu driven?
Yes, the OFS has several parameters that may be selected with a user friendly, menu driven set-up. The Control Box contains a digital display module and 4-position keypad that may be used to enter all user parameters. The keypad is shown below:
NEXT DOWN UP SET
The NEXT () key is used to accept the selection and move to the next available parameter. The SET () key is used to accept the selection and exit to operational mode. The and keys are used to move down and up to the available choices of a given parameter such as 9600 baud, 14,400 baud, etc.
5. Does the remote display give indications of transmitted or received signal strength or signal quality?
Yes, the Control Box provides both a visual and electronic indication of system diagnostics and self-tests. In the event that the OFS detects a problem such as the A or B optical signal strength being out of range, the Control Box digital display flashes a message with details about the specific problem. For customers using one of the serial data outputs, the status indicator in bytes 31 & 32 of the data string are changed from 0 to a number indicating a specific problem. In addition, the velocity data in bytes 4-7 are dashed out ---- to prevent erroneous data from being recorded at the user data acquisition system. For customers using the 4-20 ma loop option, the current is set 4 ma (0 m/s) & the diagnostic relay activated.
6. Can a serial device read results from the flow meter instead of an analog output?
Yes, the OFS comes with serial data output. The RS-232 is standard (but customer must specify output on
order). The customer may also specify both RS-232 and 4-20ma if desired. In addition, RS-485 and other formats are available as options.
7. How is the flow meter data corrected to agree with the reference system data?
A correction factor allows the user to offset the OFS velocity to match the velocity of a known standard. The OFS velocity may be increased/decreased in 1% increments using the Control box keypad or remotely over the serial interface.
8. For installations that meet the siting criteria, what accuracy and repeatability is expected?
Based on our NIST tests, the relative error was measured to be 1.1%.
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Maintenance
1. What disassembly is required to clean optical heads?
The only component requiring cleaning is the glass windows.
2. How often should optical heads be cleaned?
The time interval between window cleaning is dependent on a number of factors such as type of fuel burned, flow rates, etc. The OFS automatically warns when the windows should be cleaned by setting an advance warning error flag in byte 32 of the serial data string. When the byte is set, the user has several weeks typically to clean the windows before the system sets an actual error condition and stops reporting velocity. For customers using the 4-20 ma option, the diagnostic relay is tripped when an error condition such as dirty optics is detected. A typical cleaning interval for coal-fired gas plants is 6+ months.
3. What indications does the instrument give that the optical heads are dirty or ports blocked?
Every three seconds, the OFS performs a self-test on the received signal strength across the stack. If the readings drop to <0.1 volts, the following occurs:
RX Unit Lower LED on side of unit is turned OFF
Control Box Digital display flashes message
- Serial data string error byte set
- Diagnostic relay tripped (4-20 ma users)
4. Do any parts require factory calibration to match sensors?
No, all parts are completely interchangeable.
5. Are there any parts that cannot be replaced or calibrated in the field?
No, all OFS parts can be replaced (down to the OSi established field replaceable unit level). All FRUs are
calibrated in the factory and may be plugged into any operational OFS.
6. Are replacement parts interchangeable with each other or are devices factory matched?
All OFS parts are interchangeable in the field. For instance, any Control Box can be used with any TX Unit. In addition, the TX Unit Transmitter PCB can be interchanged with any other PCB.
7. Is a computer required for setup, troubleshooting, or maintenance?
A computer is not required for set-up, troubleshooting, or maintenance. The Control Box contains an integral digital display and keypad that allows all user functions to be performed without a PC. However, a computer may be connected either locally at the Control Box or remotely at the data acquisition site to perform these functions.
8. What test equipment is needed to setup, maintain, troubleshoot and repair your system?
No additional test equipment is required unless the Control Box is separated from the optical heads. If separated, a pair of 2-way radios or cell phones will facilitate communication during the optical alignment process.
9. What is the mean time before failure of optical heads, sensors, amplifiers, and remote displays?
Field experience with OFS and other OSi optical anemometers used at aluminum smelters suggests an MTBF > 35,000 hours.
10. How long will you guarantee the availability of spare parts?
OSi does not have a guarantee of spare parts availability. However, in our 16-year history, we have never failed to repair or replace any of our products.
11. Can additional troubleshooting data be accessed with a computer from a serial port?
A computer may be used to access troubleshooting data but the same information may be obtained without a computer by using the keypad on the control box.
12. Is there a way to visually display the signals from the optical heads for troubleshooting?
The analog signals from the RX Unit to the Control Box may be monitored using a DVM or oscilloscope at the J2 terminal block on the Receiver PCB. In addition, if the user purchases an optional laptop cable, the signals can be easily monitored on a laptop for temporary display.
13. What routine maintenance is recommended?
Recommended maintenance is semiannual and includes the following items.
Installation condition check
Visual indicator light check
Window cleaning
Auto Calibration
14. Are there any maintenance activities that might take more one person to complete?
The OFS has been designed to be installed, operated, and maintained by one person if the TX Unit, RX Unit, and Control Box are collocated on the stack.
15. Can configuration parameters be stored electronically and reloaded in the flow meter?
The user selectable configuration parameters are stored electronically in the OFS Control Box in EEROM. The EEROM is electrically erasable over 1 million times and retains its contents when power is removed. Parameters are entered using the integral keypad and digital display.
16. Are parts kept in stock?
Parts for the OFS are typically in stock due to the ongoing shipments of the product.
17. How long will it take to receive replacement parts?
If the parts are in stock, overnight shipments can guarantee next day delivery. [return to top]
Acquisition Factors
1. What parts and services are not included with the OFS?
The OFS is designed for simple installation and is available with almost everything needed for installation. The standard OFS is supplied without power cords with the assumption that the user will hardwire the system with flexible conduit. If the local conditions do not require conduit, the OFS can be supplied with power cords. In general, the user must supply electrical service (wires, conduit, etc), signal cabling & conduit from Control Box to CEM Building, conduit from RX Unit to Control Box and Control Box mounting hardware.
Note - OSi can customize the installation hardware to meet your requirements.
OSi also offers a system commissioning / user training service package that although optional, is highly recommended. One of our field engineers will come to the users site (after the user has installed the unit) to verify the installation and calibration of the OFS and to train one or more customer technical representatives in the calibration, operation, and maintenance of the OFS.
2. What system warranty is available?
OSI offers a full 12-month from date of shipment warranty.
3. Are computer interface cables included in the quote?
An optional communications cable can be included in the quote upon request.
4. Are purge air blowers, filters, and purge air ducting included in quote?
No purge air is required.
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Consumable Spare Parts
1. List the prices of those parts that should be replaced on a periodic basis.
There are no consumable spare parts in the OFS since the system has a completely solid-state, no moving part design and the optical heads are outside of the stack.
Recommended Spare Parts
1. What parts should be kept in stock to ensure monitor availability?
The major components of the OFS (TX Unit, RX Unit, and Control Box) may either be replaced in their entirety or the individual subassemblies within those major components may be replaced in the field. OSi will work with each customer to arrange the best logistics plan for the OFS deployment.
2. What is the typical price to replace or rebuild optical heads or sensors?
A typical price to rebuild one optical head is 20-30% of the replacement cost.
3. What parts warranty is available?
Normally, parts have the same 12-month warranty as the OFS system.
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