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Automated flow-recording system for field drainage monitoring—Direct data compilation of surface and subsurface drain flow
J. ugric. Engng Res.(1973)18, 31-35
Automated Monitoring-
Flow-Recording Direct
System for Field Drainage
Data Compilation
Subsurface
of Surface and
Drain Flow*
J. BoRNsrEINt ; H. A. PRESTON:; W, M. WINANT~; G. R. BENOIT~ An automatic recording console has been developed to accept water stage data from remote weirs and flumes and store the data on magnetic tape. The sensing-transmitting-cyclingrecording components can economically replace the mechanical-manual systems for converting flow events to card or tape data ready for computer analysis. A sequence of problems that had prevented operation was solved and is reported herein. 1.
Introduction
Tedious manual steps are required to analyze data recorded on FW-1 and similar water stage recorder charts. Date, zero stage, storm beginning and ending, week, month and occasionally other information must be marked on charts before conversion to card data. Chart readers and associated instruments have reduced handling and increased data reduction efficiency to some extent. Also, the use of longer-period chart drive gears has reduced frequency of chart changing, but has decreased data sensitivity. The need for a system that can sense gauge heights to 0.01 ft with the precision of direct chart reading is apparent when many recorders are in use. Automated flow recording equipment should also accept date and time, handle the existing number of stations at a desired frequency and also be capable of future expansion. Such equipment should provide labour and financial savings equal to, or exceeding, that of existing mechanical-manual systems. To accomplish this, a system was needed in which charts and chart changing, clocks and clock maintenance and conversion of data by a chart reader would be eliminated. However, ultra-sophistication of field equipment often leads to new problems requiring even more sophisticated solutions. Such equipment, to be usable, must withstand the rigours of long, cold winters, high humidity and intermittent, abrupt changes in weather. The system was needed for use on a compact, intensively instrumented field drainage area in northern Vermont. The research site with location of recorders at the interception drainage field project has been described previously.’ Consultation with a custom electronics manufacturer and with co-workers at the University of Vermont’s Instrumentation and Model Facility showed that such a system could be assembled. For example, Tromble & Enfield* had developed a partial unit for use either indoors or in a dry, mild climate, but had no comments regarding operational reliability. Another researcher had attempted automated flow recording, later deciding that too much development time was involved for his needs. Equipment developed for water-quality monitoring has similar design3 and some of the same problems. 2.
Electronic sensing hardware
The system developed for the drainage research project consists of a standard FW-1 water stage recorder with float and counterweight. Each recorder was modified by adding a 4 W, 50 k Q, one-turn, precision potentiometer onto the float wheel shaft. A buried, weather-protected, * Based on A.S.A.E. paper No. 71-583 presented at Chicago, Illinois, U.S.A. December 7-10, 1971 t Agricultural Research Service, U.S.D.A.. So. Burlington, Vermont, U.S.A. $ Instrumentation and Model Facility, University of Vermont, Burlington, U.S.A. Experiment Station)
31
(Journal
Series Paper No. 285, Vermont Agricultural
32
SYSTEM
FOR
FIELD
DRAINAGE
MONITORINCi
Teflon-coated pair of individual No. 20 wires carries the signal from each of 36 recording stations to the central data processor-recorder, a system referred to as the ARC. 2.1. Flow station recorder mod$cations Potentiometers on the FW-1 recorders are calibrated to give zero output at zero stages of the float (the no-flow condition at the H-flumes or 30” notch weirs, respectively). The single-turn potentiometers have a linear range of 0.92 ft scaled to read flow through the B-in weirs, 12- and 18-in H flumes. Under normal operation when there has been no flow for a period, water drains down or evaporates from the float wells. This causes the pen (operating on a reversing gear) to move above zero, giving a flow signal that the ARC would read. To prevent the negative gear shaft rotation, a mechanical stop was placed on the float tape that holds the potentiometer on zero for float levels at zero or below. 2.2. Recording console-components and functions At the ARC an operational amplifier provides a voltage signal to each station in proper sequence. There are 36 recorder stations, one each for 20 subsurface and 16 surface drains. A 40-terminal double crossbar scanner accepts gauge height data (Fig. Z). Two of the terminals are for date and time and 2 for calibration. A visual readout provides numerical gauge height and station identification in sequence. Fig. 2 shows the overall system layout; Fig. 3 detailed ARC electronics. Reed relays
* Statlan No. I 0
z
---+
Control and tope systems
“A” to “D” Converter
Control and taps systems scanner
Fig. I. Detail of reed relays and crossbar scanner (only relays to stations I and 40 shown)
The gauge height data are accepted by the crossbar scanner and sensed by an analog to digital converter. A 3-s sensing time is assigned to each station. The signals are processed by the A-D converter through the functions of control, timing and conversion to B-channel binary representation, acceptable by the Kennedy 9-track digital tape recorder. To limit unnecessary use of magnetic tape when no flow is occurring from any of the drains, the tape recorder shuts off automatically. Flow in any one drain requires continuous cycling through the stations and data transmission to tape. When all show no flow, the tape recorder stops. The scanning sensor continues to monitor the flow stations, instantly recording when flow occurs at any one or more stations. To maintain the true time base, the calibration, date and time points continue to function.
J.
BORNSTEIN;
H.
A.
PRESTON;
W.
M.
G.
WINANT
R.
33
BENOIT
Specifically, when the system is recording from only one station, the scanning sensor begins counting no-flow stations. When it reaches 36 consecutive stations showing less than 0.01 ft of gauge height, the tape recorder stops. Each time it reaches a flowing station, the reset counter returns to zero and again starts counting toward 36.
FW-I Reco~a~r r,tatlOnS (36;
I 36 Non- arounded
1 I 1
5w Preclslon potentiometer
t I
Field
I
40 Posltlon recording system
Pairs
protectors
AMP 1
I I
j
Selects one posltlon every 3s l-36 37 38 39 00
Fig. 2. General layour of electronic
Statlons Calibrate Date Time Calibrate
system from flow sensing to recording
8
Chanyl
tape Date
Dtsplay ) l/6 MI”
Clock IHZ
40/2 MI” Advance Scan Tape lnhlblt
Tape print advance bar scanner
Cross
Ready for date time and data
End of record advance
I
Fig. 3.
Detailed
circuitry
of aatomated
recording
console
> r
34
SYSTEM
3.
FOR
FIELD
DRAINAGE
MONITORING
Problems of automated recording systems
Exposure of electronic equipment to environmental extremes and variations compiles problems that mask each other in sequence. An automated flow recording system for the field can be operational only after reaching the problem series end point. The system functioned smoothly under laboratory conditions, but several unexpected types of interference and malfunctions occurred in the field installation. For example, the FW-1 recorders were protected from wind and rain but not from snow, temperature and humidity changes. Dust accumulation combined with moist instrument surfaces proved to be a definite hazard to equipment operation. Other problems in the series that inhibited ARC system operation included soil-heating-cable noise. lightning, d.c. potential at shelters and power outages. 3.1. Moisture To reduce the humidity and dust interference, potentiometers on the FW-l’s were sprayed with a moisture proof film to keep them clean and dry. The protective spray was also applied to the analog-to-digital converter in the ARC itself. 3.2. Electrical noise One power use has been to operate thermostatically controlled, insulated 30- and 40-W soilheating cables buried around each instrument shelter. 4 These helped protect against freeze-thaw cycles that heaved instrument shelters, but the heating cable operation generated noise in the recording system. An operational amplifier was added and this allowed operation of the heating systems while collecting flow data. The op-A eliminated common mode effects. Instead of reading resistance changes, the ARC switched to voltage sensing, cancelling a.c. interference and allowing the d.c. analog signal to be processed. 3.3.
Lightning and electrolysis
Data acquisition was improved further by eliminating the parallel lines from all stations that had been feeding into the ARC at all times. Adding double-pole, double-throw reed switches (Fig. I) disconnected all wires to the ARC except those to the station being monitored. It allowed the system to read only one pair of wires from the recorders at a time, instead of the 36 pairs. This also reduced danger of secondary lightning charges and eliminated the d.c. potential generated by the dissimilar metals used in shelter construction. Tile recorder shelters of aluminium attached to a zinc-coated steel well created electrolysis and the d.c. output. Previously, the common terminal with wires attached from all stations amplified the d.c. voltage, particularly in wet weather. 3.4.
Secondary charges
Secondary charges from lightning frequently disabled the system. Preventive measures included a sheet aluminium cap over each wooden flume shelter tied to a standard 8 ft ground rod. Ground rods were installed and tied to the aluminium shelters at subsurface drain recorders. The double-throw reed switches reduced the danger by interrupting secondary charges that might be generated in the buried cables. Further, lightning protection was assured by adding Siemens gas-filled surge voltage protectors on line at each of the potentiometers to ground, Fig. 2, and at the op-A on the line side. 3.5.
Power outages
The frequency of electrical storms and early and late winter snows causes several power cuts each year aside from direct ARC impact. Another problem has been the scheduled power shutdowns that have occurred each year to permit special work on utility facilities. These power cuts from the outside source are still a problem. Whenever the power goes off, the ARC shuts
J.
BORNSTEIN;
H.
A.
PRESTON;
W.
M.
WINANT;
G.
R.
BENOlT
35
down. It must be restarted manually when power returns. We must reset the time and date clock (a binary system of lights) and advance the tape recorder to establish the proper file gap. 4. Proposed improvement To avoid power loss effects we propose supplying d.c. voltage through an inverter. Line voltage would maintain charge on a storage battery and date and time could be carried by a crystal clock. Then, with power off, the system could continue to record flow data without interruption. This would provide us with 2 h operation without outside power-longer than any outage experienced to date. When power was restored it would automatically recharge the battery to bring it back to full power. This inverter system would be similar to an automobile generator-battery hookup. 5.
Summary and conclusions
For a long-term intensive hydrologic or drainage research project with many flow-recording stations, an automatic data recording system is extremely worthwhile. However, close supervision and follow-up, particularly during initial stages of use, careful maintenance and continuous monitoring to upgrade the equipment are necessary and advisable. As emphasized by Blakey,3 “The single most important factor in monitor operations is trained field personnel.” When fully adapted to the specific field conditions, an effective system of data sensing will transmit a precise, detailed record to a computer-compatible magnetic tape. The system described herein has functioned successfully throughout the autumn of 1971. The difficulties of maintaining the system in a cold climate even during moderate summer months still creates problems, but the quality of data and the reduction in manual handling enhance the ARC as a practical water resource research tool. We find that the system as it was operated reached a level of reliability and precision equal to the clock driven, FW-1 recorder with pen and ink data trace. REFERENCES
Bornstein, J.; Benoit, G. R. Subsurface drain and discharge comparisons on a sloping fragipan soil. Trans. Am. Sot. agric. Engrs, 1967 10 (5) 590 2 Tromble, J. M.; Enfield, C. G. Adapting analog water stage recorders to digital data acquisition systems. Agric. Engng, St Joseph, Mich., 1971 52 (2) 80 3 Blakey, J. F. Design of an automatic monitoring system. Proc. National Symp. on Data and Instrumentation for Water Quality Mgmt Conf. of State Sanitary Engrs and Wise. Univ. July 21-23, 1970 Madison, Wise. p. 243. 4 Bornstein, J.; Alberts, R. R.; Benoit, G. R. Insulated soil-heating system to prevent frost-heaving of ,field instrumentation. J. agric. Engng Res., 1969 14 (1) 100 ’
Automated Monitoring-
Flow-Recording Direct
System for Field Drainage
Data Compilation
Subsurface
of Surface and
Drain Flow*
J. BoRNsrEINt ; H. A. PRESTON:; W, M. WINANT~; G. R. BENOIT~ An automatic recording console has been developed to accept water stage data from remote weirs and flumes and store the data on magnetic tape. The sensing-transmitting-cyclingrecording components can economically replace the mechanical-manual systems for converting flow events to card or tape data ready for computer analysis. A sequence of problems that had prevented operation was solved and is reported herein. 1.
Introduction
Tedious manual steps are required to analyze data recorded on FW-1 and similar water stage recorder charts. Date, zero stage, storm beginning and ending, week, month and occasionally other information must be marked on charts before conversion to card data. Chart readers and associated instruments have reduced handling and increased data reduction efficiency to some extent. Also, the use of longer-period chart drive gears has reduced frequency of chart changing, but has decreased data sensitivity. The need for a system that can sense gauge heights to 0.01 ft with the precision of direct chart reading is apparent when many recorders are in use. Automated flow recording equipment should also accept date and time, handle the existing number of stations at a desired frequency and also be capable of future expansion. Such equipment should provide labour and financial savings equal to, or exceeding, that of existing mechanical-manual systems. To accomplish this, a system was needed in which charts and chart changing, clocks and clock maintenance and conversion of data by a chart reader would be eliminated. However, ultra-sophistication of field equipment often leads to new problems requiring even more sophisticated solutions. Such equipment, to be usable, must withstand the rigours of long, cold winters, high humidity and intermittent, abrupt changes in weather. The system was needed for use on a compact, intensively instrumented field drainage area in northern Vermont. The research site with location of recorders at the interception drainage field project has been described previously.’ Consultation with a custom electronics manufacturer and with co-workers at the University of Vermont’s Instrumentation and Model Facility showed that such a system could be assembled. For example, Tromble & Enfield* had developed a partial unit for use either indoors or in a dry, mild climate, but had no comments regarding operational reliability. Another researcher had attempted automated flow recording, later deciding that too much development time was involved for his needs. Equipment developed for water-quality monitoring has similar design3 and some of the same problems. 2.
Electronic sensing hardware
The system developed for the drainage research project consists of a standard FW-1 water stage recorder with float and counterweight. Each recorder was modified by adding a 4 W, 50 k Q, one-turn, precision potentiometer onto the float wheel shaft. A buried, weather-protected, * Based on A.S.A.E. paper No. 71-583 presented at Chicago, Illinois, U.S.A. December 7-10, 1971 t Agricultural Research Service, U.S.D.A.. So. Burlington, Vermont, U.S.A. $ Instrumentation and Model Facility, University of Vermont, Burlington, U.S.A. Experiment Station)
31
(Journal
Series Paper No. 285, Vermont Agricultural
32
SYSTEM
FOR
FIELD
DRAINAGE
MONITORINCi
Teflon-coated pair of individual No. 20 wires carries the signal from each of 36 recording stations to the central data processor-recorder, a system referred to as the ARC. 2.1. Flow station recorder mod$cations Potentiometers on the FW-1 recorders are calibrated to give zero output at zero stages of the float (the no-flow condition at the H-flumes or 30” notch weirs, respectively). The single-turn potentiometers have a linear range of 0.92 ft scaled to read flow through the B-in weirs, 12- and 18-in H flumes. Under normal operation when there has been no flow for a period, water drains down or evaporates from the float wells. This causes the pen (operating on a reversing gear) to move above zero, giving a flow signal that the ARC would read. To prevent the negative gear shaft rotation, a mechanical stop was placed on the float tape that holds the potentiometer on zero for float levels at zero or below. 2.2. Recording console-components and functions At the ARC an operational amplifier provides a voltage signal to each station in proper sequence. There are 36 recorder stations, one each for 20 subsurface and 16 surface drains. A 40-terminal double crossbar scanner accepts gauge height data (Fig. Z). Two of the terminals are for date and time and 2 for calibration. A visual readout provides numerical gauge height and station identification in sequence. Fig. 2 shows the overall system layout; Fig. 3 detailed ARC electronics. Reed relays
* Statlan No. I 0
z
---+
Control and tope systems
“A” to “D” Converter
Control and taps systems scanner
Fig. I. Detail of reed relays and crossbar scanner (only relays to stations I and 40 shown)
The gauge height data are accepted by the crossbar scanner and sensed by an analog to digital converter. A 3-s sensing time is assigned to each station. The signals are processed by the A-D converter through the functions of control, timing and conversion to B-channel binary representation, acceptable by the Kennedy 9-track digital tape recorder. To limit unnecessary use of magnetic tape when no flow is occurring from any of the drains, the tape recorder shuts off automatically. Flow in any one drain requires continuous cycling through the stations and data transmission to tape. When all show no flow, the tape recorder stops. The scanning sensor continues to monitor the flow stations, instantly recording when flow occurs at any one or more stations. To maintain the true time base, the calibration, date and time points continue to function.
J.
BORNSTEIN;
H.
A.
PRESTON;
W.
M.
G.
WINANT
R.
33
BENOIT
Specifically, when the system is recording from only one station, the scanning sensor begins counting no-flow stations. When it reaches 36 consecutive stations showing less than 0.01 ft of gauge height, the tape recorder stops. Each time it reaches a flowing station, the reset counter returns to zero and again starts counting toward 36.
FW-I Reco~a~r r,tatlOnS (36;
I 36 Non- arounded
1 I 1
5w Preclslon potentiometer
t I
Field
I
40 Posltlon recording system
Pairs
protectors
AMP 1
I I
j
Selects one posltlon every 3s l-36 37 38 39 00
Fig. 2. General layour of electronic
Statlons Calibrate Date Time Calibrate
system from flow sensing to recording
8
Chanyl
tape Date
Dtsplay ) l/6 MI”
Clock IHZ
40/2 MI” Advance Scan Tape lnhlblt
Tape print advance bar scanner
Cross
Ready for date time and data
End of record advance
I
Fig. 3.
Detailed
circuitry
of aatomated
recording
console
> r
34
SYSTEM
3.
FOR
FIELD
DRAINAGE
MONITORING
Problems of automated recording systems
Exposure of electronic equipment to environmental extremes and variations compiles problems that mask each other in sequence. An automated flow recording system for the field can be operational only after reaching the problem series end point. The system functioned smoothly under laboratory conditions, but several unexpected types of interference and malfunctions occurred in the field installation. For example, the FW-1 recorders were protected from wind and rain but not from snow, temperature and humidity changes. Dust accumulation combined with moist instrument surfaces proved to be a definite hazard to equipment operation. Other problems in the series that inhibited ARC system operation included soil-heating-cable noise. lightning, d.c. potential at shelters and power outages. 3.1. Moisture To reduce the humidity and dust interference, potentiometers on the FW-l’s were sprayed with a moisture proof film to keep them clean and dry. The protective spray was also applied to the analog-to-digital converter in the ARC itself. 3.2. Electrical noise One power use has been to operate thermostatically controlled, insulated 30- and 40-W soilheating cables buried around each instrument shelter. 4 These helped protect against freeze-thaw cycles that heaved instrument shelters, but the heating cable operation generated noise in the recording system. An operational amplifier was added and this allowed operation of the heating systems while collecting flow data. The op-A eliminated common mode effects. Instead of reading resistance changes, the ARC switched to voltage sensing, cancelling a.c. interference and allowing the d.c. analog signal to be processed. 3.3.
Lightning and electrolysis
Data acquisition was improved further by eliminating the parallel lines from all stations that had been feeding into the ARC at all times. Adding double-pole, double-throw reed switches (Fig. I) disconnected all wires to the ARC except those to the station being monitored. It allowed the system to read only one pair of wires from the recorders at a time, instead of the 36 pairs. This also reduced danger of secondary lightning charges and eliminated the d.c. potential generated by the dissimilar metals used in shelter construction. Tile recorder shelters of aluminium attached to a zinc-coated steel well created electrolysis and the d.c. output. Previously, the common terminal with wires attached from all stations amplified the d.c. voltage, particularly in wet weather. 3.4.
Secondary charges
Secondary charges from lightning frequently disabled the system. Preventive measures included a sheet aluminium cap over each wooden flume shelter tied to a standard 8 ft ground rod. Ground rods were installed and tied to the aluminium shelters at subsurface drain recorders. The double-throw reed switches reduced the danger by interrupting secondary charges that might be generated in the buried cables. Further, lightning protection was assured by adding Siemens gas-filled surge voltage protectors on line at each of the potentiometers to ground, Fig. 2, and at the op-A on the line side. 3.5.
Power outages
The frequency of electrical storms and early and late winter snows causes several power cuts each year aside from direct ARC impact. Another problem has been the scheduled power shutdowns that have occurred each year to permit special work on utility facilities. These power cuts from the outside source are still a problem. Whenever the power goes off, the ARC shuts
J.
BORNSTEIN;
H.
A.
PRESTON;
W.
M.
WINANT;
G.
R.
BENOlT
35
down. It must be restarted manually when power returns. We must reset the time and date clock (a binary system of lights) and advance the tape recorder to establish the proper file gap. 4. Proposed improvement To avoid power loss effects we propose supplying d.c. voltage through an inverter. Line voltage would maintain charge on a storage battery and date and time could be carried by a crystal clock. Then, with power off, the system could continue to record flow data without interruption. This would provide us with 2 h operation without outside power-longer than any outage experienced to date. When power was restored it would automatically recharge the battery to bring it back to full power. This inverter system would be similar to an automobile generator-battery hookup. 5.
Summary and conclusions
For a long-term intensive hydrologic or drainage research project with many flow-recording stations, an automatic data recording system is extremely worthwhile. However, close supervision and follow-up, particularly during initial stages of use, careful maintenance and continuous monitoring to upgrade the equipment are necessary and advisable. As emphasized by Blakey,3 “The single most important factor in monitor operations is trained field personnel.” When fully adapted to the specific field conditions, an effective system of data sensing will transmit a precise, detailed record to a computer-compatible magnetic tape. The system described herein has functioned successfully throughout the autumn of 1971. The difficulties of maintaining the system in a cold climate even during moderate summer months still creates problems, but the quality of data and the reduction in manual handling enhance the ARC as a practical water resource research tool. We find that the system as it was operated reached a level of reliability and precision equal to the clock driven, FW-1 recorder with pen and ink data trace. REFERENCES
Bornstein, J.; Benoit, G. R. Subsurface drain and discharge comparisons on a sloping fragipan soil. Trans. Am. Sot. agric. Engrs, 1967 10 (5) 590 2 Tromble, J. M.; Enfield, C. G. Adapting analog water stage recorders to digital data acquisition systems. Agric. Engng, St Joseph, Mich., 1971 52 (2) 80 3 Blakey, J. F. Design of an automatic monitoring system. Proc. National Symp. on Data and Instrumentation for Water Quality Mgmt Conf. of State Sanitary Engrs and Wise. Univ. July 21-23, 1970 Madison, Wise. p. 243. 4 Bornstein, J.; Alberts, R. R.; Benoit, G. R. Insulated soil-heating system to prevent frost-heaving of ,field instrumentation. J. agric. Engng Res., 1969 14 (1) 100 ’