A portable field data logger-penetrometer interface

A portable field data logger-penetrometer interface

Computers and Electronics in Agriculture, 3 (1989) 255-261 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands 255 A Portable...

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Computers and Electronics in Agriculture, 3 (1989) 255-261 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

255

A Portable Field Data L o g g e r - P e n e t r o m e t e r Interface S.W. WAGNER l, J.F. JOHNSON 2 and W.B. VOORHEES 1

1USDA Agricultural Research Service, Morris, MN 56267 (U.S.A.) 2University of Minnesota, Morris, MN 56267 (U.S.A.) (Accepted 3 October 1988)

ABSTRACT Wagner, S.W., Johnson, J.F. and Voorhees, W.B., 1989. A portable field data logger-penetrometer interface. Comput. Electron. Agric., 3: 255-261. A Bush Recording Soil Penetrometer was interfaced to a portable field data logger (The Polycorder Electronic Notebook), Model 516C-634, manufactured by Omnidata International. Penetrometer data were automatically read and transferred, under microprocessor control, to the portable data logger via an interface cable and appropriate software. The electronic interface linking the two instruments and the interface software is discussed. Use of the system reduced the required field data collection time by approximately 50 % and minimized the chance for human error in the data collection process. The system also allows for efficient and accurate transfer of recorded field data to a separate desk-top microcomputer tbr subsequent analysis.

INTRODUCTION

Penetrometers have been used for varied applications, including soil strength assessments, trafficability predictions, and assessment of soil compaction and impedance to root penetration (Perumpral, 1987). Changes in penetrometer resistance with soil depth and time have been used as an indicator of the extent and persistence of soil compaction caused by wheel traffic (Voorhees, 1983; Johnson et al., 1986; Voorhees et al., 1986). Voorhees et al. (1975) related the growth and elongation rates of plant roots to soil penetrometer resistance. Due to the natural soil variability, a large number of readings are required to obtain Contribution from the North Central Soil Conservation Research Laboratory, Agricultural Research Service, USDA, Morris, MN 56267; in cooperation with the Minnesota Agricultural Experiment Station, Sci. J. Series 15,898. Trade names and company names are included for the benefit of the reader and do not imply any endorsement or preferential treatment of the product listed by the U.S. Department of Agriculture.

0168-1699/89/$03.50

© 1989 Elsevier Science Publishers B.V.

256 a reliable value of penetrometer resistance under field conditions. It is desirable to collect these data with minimal recording errors and in a minimum amount of time. The penetrometer currently being used in tillage-compaction research at Morris, Minnesota, is the Bush Recording Soil Penetrometer. This penetrometer was developed by the Scottish Institute of Agricultural Engineering (Anderson et al., 1980). The penetrometer stores up to 15 values (depths) of penetration resistance per penetration in an internal buffer. Since the penetrometer will store only 15 values, the data must be read and recorded after every penetration. To satisfy requirements of speed and accuracy in the data collection process, various approaches have been used. The penetrometer was originally interfaced by the manufacturer to a Hewlett-Packard 97S programmable desk-top calculator. The calculator controlled the transfer of the 15 values from the buffer in the penetrometer to internal memory of the calculator. However, due to the limited memory of the calculator, no values were recorded in memory but were instead printed by a thermal printer. This method was quite time-consuming. O'Sullivan et al. (1982) interfaced the penetrometer to a 'Datamyte' portable data entry terminal. This removed the memory restriction but required a special converter mounted on the penetrometer to convert the parallel BCD output of the penetrometer to a serial input compatible with the Datamyte. The objective of this paper is to describe an interface that permits rapid and direct transfer of data from the penetrometer to a portable field data logger. THE PENETROMETER The 15 soil resistance values stored in the penetrometer's internal buffer represent the digital equivalent of an analog signal output from a load-cell transducer. These values (0 to 500 N) are stored in the penetrometer in a twodigit BCD number from 0 to 99. The resistance values for a penetration can be viewed by the operator on the penetrometer liquid crystal display by 'clocking' through the penetrometer internal memory. In addition to being displayed the resistance values are provided as BCD output at the penetrometer interface - a DB25 connector on the penetrometer (Fig. 1). Also available on the penetrometer interface connector is a 'load calculator' control output and a 'data request' control input. INTERFACE TECHNIQUE An interface cable connects the Polycorder sensor interface to the penetrometer interface connector (Fig. 1). The nine digital inputs and one of the five digital outputs available on the Polycorder sensor interface were utilized. The BCD digits' output from the penetrometer are input to the Polycorder via the

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Fig. 1. I n t e r ~ c e c o n n e c t i o n s ,

sensor interface (digital inputs 1-8). Digital input 9 is utilized to sense the 'load calculator' penetrometer output. This penetrometer output consists of the normally closed 'load calc.' request switch ($4, Fig. 2) in series with the penetrometer handshake circuit control output (Q, Fig. 2). The penetrometer handshake circuit consists of a monostable multivibrator or 'one-shot' which controls the timing of the transfer of data to the data logger. The handshake circuit provided in the penetrometer is utilized so that no external circuitry is required to control the timing of data transfers. The timing chart for the interface is shown in Fig. 3. After a penetration is completed, the operator momentarily depresses the 'load calculator' switch ($4, Fig. 2) of the penetrometer, signaling the microprocessor in the data logger to start the transfer of data. Thus the microprocessor is programmed to poll digital input 9 to determine when the operator requests a data transfer. The operator's request signals the microprocessor to repeatedly toggle the one-shot by applying a pulse via the Polycorder sensor interface (digital output 1) to the 'data request' penetrometer input (Fig. 2 ) until all 15 values have been transferred. In the quiescent state of the one-shot the Q output is low and the complemented output (Q) is high. Applying the 'data request' pulse causes the oneshot to enter the active state (Q is low) for a duration of time equal to the time constant of the one-shot. The handshake control output (Q, Fig. 2) goes high

258 Polycorder Sensor Interface Digital Output 1 Digital Input 9

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Fig. 3. Interface timing diagram.

and signals the penetrometer circuitry to output a penetration resistance value from the buffer. The microprocessor polls the 'load calc' line for the duration of the one-shot pulse. When the output Q goes high, the microprocessor reads the data and stores the information in a file (Fig. 3). 'Data request' pulses are applied until all data for a penetration have been transferred and recorded.

259 LINE OPCODE I. 20 2. 12 3. 31 4. 43 5. 61 6. 43 7. 61 8. 20 9. 29 I0. 20 ii. 29 12. ii 13. 20 14. 29 15. 20 16. 29 17. 51 18. 3 19. 26 20. 52 21. 26 22. 52 23. 26 24. 52 25. 51 26. 2 27. 50 28. 14 29. 75 30. 26 31. 82 32. 86 33. 75 34. 26 35. 81 36. 14 37. 15 38. 75 39. 26 40. 96 41. 75 42. 15 43. 79 44. 77 45. 61 46. 57 47. 75 48. 26 49. 80 50. 3 51. 1 52. 0

MNEMONIC CDS WID GSB ENT IOP ENT ICP CDS VUM CDS VUM DLY CDS VUM CDS VUM IN9 JNZ CON OUT CON OUT CON OUT IN9 JPZ INP STO PSH CON DIV INT PSH CON MLT STO RCL PSH CON AND PSH RCL ADD STF ICP RLC PSH CON SUB JNZ JMP END

PARAMETER 0,31 16 DATAFILE

COMMENTS • clear display • set d i s p l a y w i d t h ; open d a t a file s u b r o u t i n e ; enter p l o t # ; point to n e x t c o l u m n • enter tillage t r e a t m e n t ; point to next c o l u m n 0,31 ; clear d i s p l a y PRESS "RESET STORE" & "RESET DEPTH" 16,15 ; p o s i t i o n cursor T H E N P E N E T R A T E SOIL 20 ; d e l a y 2 seconds 0,31 ; clear display PRESS "RESET DEPTH" 16,15 ; p o s i t i o n cursor PRESS "LOAD CALC." ; input load calc. status 17 ; poll until user p r e s s e s 0 ; switch $4, "LOAD CALC." ; i ; send r e q u e s t data p u l s e 0

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start of n e w line? r e q u e s t m o r e data if line is not f i l l e d next plot

260 subprogram i. 20 2 12 3 29 4 20 5 67 6 64 7 0

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0 32 ; clear the d i s p l a y 16 ; display width W H I C H D A T A FILE? 16 16 ; enter file name ; open data file ; r e t u r n from s u b r o u t i n e

Fig. 4. D a t a collection p r o g r a m listing.

SOFTWARE The data logging program was written in 'Polycode' (Omnidata International, 1985), a programming language specific to the Polycorder computer. Polycode has similar features to assembly language and some capabilities of a 'higher level' language such as Basic. Data are stored in the Polycorder in a file divided into a matrix of fields identified by page, line, and column numbers. The data file format is specified by the user and stored in a Polycorder format file. A program file contains the list of instructions which perform the data collection. The data collection program listing (Fig. 4) is provided for reference. The program begins by opening a data file for data storage. The user is prompted to enter a plot identification and tillage treatment. The program executes a polling loop until a 'load calc.' signal is received. At this time the user must ready the penetrometer by pressing the 'reset store' and 'reset depth' switches on the penetrometer. Next a penetration measurement is made. The user then presses the 'rest depth' and 'load calc.' switches on the penetrometer. When the microprocessors senses the 'load calc.' signal, the program continues by sending a request data pulse to the penetrometer and loops until the penetrometer presents the data at its output ('load calc.' goes high). Data presented at the output are read and converted from parallel BCD to decimal and stored in a file. This handshaking process is repeated until all data have been transferred (i.e., all columns of a line in the data file are filled). When all data have been transferred, the program allows the user to enter the next plot and tillage treatment for another penetration. The buffer contents are electronically transferred to the data logger in 2.8 s, while an experienced operator requires 25 s to record the buffer contents by manually keying data into the data logger. The time required for collection of field data will depend on many factors, including experimental design and rate of penetration. CONCLUSION The electronic interface between a penetrometer and field data logger for rapid and direct transfer of field data was discussed. Use of the system in til-

261 l a g e - c o m p a c t i o n r e s e a r c h a t M o r r i s , M i n n e s o t a d u r i n g t h e 1987 g r o w i n g seas o n g r e a t l y r e d u c e d field d a t a c o l l e c t i o n t i m e , m i n i m i z e d t h e c h a n c e f o r h u m a n e r r o r in t h e d a t a c o l l e c t i o n p r o c e s s , a n d a l l o w e d f o r e a s y t r a n s f e r o f field d a t a to a m i c r o c o m p u t e r f o r f u r t h e r a n a l y s i s .

REFERENCES Anderson, G., Pigeon, J.D., Spencer, H.B. and Parks, R., 1980. A hand-held recording penetro meter for soil studies. J. Soil Sci., 31: 279-296. Johnson, J.F., Voorhees, W.B. and Randall, G.W., 1986. Subsoiling effects on soil penetrometer resistance and yield of corn (Zea mays L.). Agron Abstr., p. 244. Omnidata International, 1985. Polycorder Electronic Notebook Operators Manual. Omnidata I n ternational, Inc., Logan, UT, 278 pp. O'Sullivan, M.F., Dickson, J.W., Henshall, J.K. and Anderson, G., 1982 The use of a solid-state data collector interfaced to a 'bush' digital recording soil penetrometer. Dep. Note SIN/348, Scottish Institute for Agricultural Engineering, Penicuik, Scotland, 12 pp. Perumpral, J.V., 1987. Cone penetrometer applications - - a review. Trans. ASAE, 30: 939-944. Voorhees, W.B., 1983. Relative effectiveness of tillage and natural forces is alleviating wheelinduced soil compaction. Soil Sci. Soc. Am. J., 47: 129-133. Voorhees, W.B., Farrell, D.A. and Larson, W.E., 1975. Soil strength and aeration effects on root elongation. Soil Sci. Soc. Am. Proc., 39: 948-953. Voorhees, W.B., Nelson, W.W. and Randfall, G.W., 1986. Extent and persistence of subsoil compaction caused by heavy axle loads. Soil Sci. Soc. Am. J., 50: 428-433.