Shelled corn moisture tester

Apparatus for testing shelled corn in a combine storage tank during harvesting includes a plurality of charged electrodes each in the form of an elongated rod arranged in a spaced manner and positioned in a lower portion of the combine storage tank to be completely encompassed by the shelled corn. The electrodes are coupled to a moisture meter located in the combine cab allowing the operator to determine the moisture content of the corn crop at harvest. The moisture meter is easily disconnected from the electrodes and removed from the combine to permit moisture testing of corn kernels while still on the cob prior to harvest.

BACKGROUND OF THE INVENTION 
The present invention relates to electrical moisture testers for measuring 
the moisture content of shelled corn in a combine. 
Electrical moisture testers for measuring the moisture content of vegetable 
matter, and in particular grains, are well known in the art. Most moisture 
testers operate on the principal that the electrical properties (namely, 
resistance or resistivity) of vegetable matter vary with the moisture 
content of the matter. 
Some moisture testers, especially those for measuring grains, are designed 
to take bulk measurements after the grain or other crop has been harvested 
and is in storage. Such bulk measuring devices are not particularly useful 
or convenient in helping a farmer determine when to harvest the crop, or a 
seed corn company in determining "dry down" time of a new hybrid seed 
under development. 
It is known that the relationship between cob moisture and the moisture 
content of corn kernels on the cob varies substantially with different 
corn genotypes, different moisture levels, and even with the weather. 
Thus, cob moisture cannot generally be correlated with corn kernel 
moisture. It is also known that the moisture content of the husk can 
influence the value of the moisture reading obtained, especially when a 
test is conducted in the field while the ear is still on the plant. 
A moisture tester designed to estimate the moisture content of corn kernels 
on the cob is disclosed in an article entitled An Electronic Probe For 
Estimating Ear Moisture Content of Maize (Kang, et al, Crop Science, Vol. 
18, Nov.-Dec. 1978, pp. 1083-1084). That device uses a pair of spaced 
needle-shaped conductors which are applied to penetrate the husk, kernels 
and cob. The moisture meter then signals the relative magnitude of the 
electrical resistance of the cob, kernels and husk in contact with the 
needle conductors. 
U.S. Pat. No. 4,954,783, issued Sep. 4, 1990 in the name of the present 
inventor, discloses an apparatus and method for testing the moisture 
content of corn kernels on an ear of corn. The apparatus includes an ear 
cradle, a pair of electrode blades, and a circuit for measuring a 
moisture-dependent electrical property of the corn kernels. The major 
advantages of this device are that it is versatile, highly portable, 
reliable, accurate and inexpensive. The present invention contemplates 
even greater versatility and convenience for the farmer using my device. 
It is important for the farmer to know the moisture content of corn at 
harvest. It has been estimated that the cost of drying corn is reduced by 
approximately 21/2.cent. per bushel per percentage point of moisture 
content down to approximately 15%. Thus, the ability to accurately measure 
corn moisture content allows the farmer to determine the optimum time for 
harvest as well as to select which of different varieties of corn to 
harvest depending upon moisture content. Once the farmer has made his 
preliminary determination to harvest a field, he has no way to assure 
himself that his pre-harvest tests were reliable unless, after harvesting 
the first few bushels, he takes a sample back to his shop for bulk testing 
(requiring another instrument). 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide accurate 
moisture testing of corn as it is harvested. 
It is another object of the present invention to provide a corn moisture 
testing arrangement which allows for the accurate determination of kernel 
moisture content either on an ear of corn or after shelling in bulk form. 
Yet another object of the present invention is to provide a shelled corn 
moisture tester for use by a commercial corn farmer which is inexpensive, 
easily installed in and removed from a combine, and permits the farmer to 
quickly and accurately determine the moisture content of the corn crop. 
A further object of the present invention is to provide for the in-field 
testing of corn crop moisture content either in shelled bulk form or in 
individual kernels prior to removal from an ear of corn. 
The moisture measurement of the present invention is useful, not so much 
because of its definitive accuracy (which can be verified or confirmed in 
a laboratory setting), but because of its convenience and versatility, and 
because it provides a reliable, repeatable, quantitative measure with 
sufficient accuracy that a farmer may use it in the field to measure the 
moisture content of corn on the cob; and he may use the same measuring 
instrument to connect the electrodes permanently mounted in his combine to 
gain a further measure of the moisture content of the shelled or bulk corn 
as he begins to harvest a particular field and each time he begins to fill 
the combine anew. 
The present invention thus provides the farmer with the ability to 
accurately ascertain corn moisture content while the corn is in the field 
in order to determine the proper time for harvesting. It also permits him 
to use the same electronic measuring instrument to measure the moisture 
content of the corn in bulk form by means of a permanently mounted sensor 
arrangement in the combine during harvest. This is particularly important 
in the case of contract growers to provide a better measure of the value 
of a load of harvested corn. 
Other features and advantages of the present invention will be apparent to 
persons skilled in the art from the following detailed description of a 
preferred embodiment accompanied by the attached drawings wherein 
identical reference numerals will refer to like parts in the various views 
.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, there is shown in simplified combined schematic and 
block diagram form a shelled corn moisture tester 10 for use in a combine 
12 in accordance with the present invention. FIG. 2 is a sectional view of 
a portion of the corn moisture tester 10 shown in FIG. 1 taken along site 
line 2--2 therein. The combine includes a storage tank 14 and a cab 16. 
The combine storage tank is comprised of a plurality of side walls 14a-14d 
and a floor, or bottom, 14e, and is open at the top to receive corn 
removed from the corn husk and cob by various grain separation stages 
which are not shown in the figure for simplicity. 
The combine cab 16, which is shown in simplified block diagram form, 
includes various controls manipulated by the combine operator which are 
also not shown for simplicity. The combine 12 itself further typically 
includes a forward header assembly and an aft drive and processing section 
which are also not shown in the figure for simplicity. The header assembly 
typically includes a plurality of spaced corn or row crop heads which are 
adapted for engaging the crops and removing the grain therefrom. The thus 
removed grain, in combination with crop residue such as husks in the case 
of corn harvesting, are then automatically delivered to the aft processing 
and drive portion of the combine. In addition to housing the source of 
propulsion, such as a diesel engine, and operator controls within the 
combine cab 16, the aft portion of the combine also includes a complicated 
threshing system for further separating the grain from the crop residue 
and for offloading loading the thus separated grain from the combine into 
a transport port vehicle such as a truck. Following separation of the 
grain from the crop residue, the grain is temporarily deposited in the 
combine storage tank 14 for subsequent off-loading. The crop residue is 
then exhausted from an aft portion of the combine and deposited in the 
field being harvested. 
The shelled corn moisture tester 10 includes a plurality of spaced, 
elongated, rod-like electrodes 18a-18d disposed within a lower portion of 
the combine storage tank 14. Each of the electrodes 18a-18d is preferably 
comprised of an electrically conductive phosphor-bronze composition. The 
electrodes 18a-18d are coupled to and supported by a pair of spaced 
support members 32a and 32b. The support members 32a, 32b maintain the 
electrodes 18a-18d in fixed, spaced relation within a lower portion of the 
combine storage tank 14. Each of the support members 32a, 32b is 
preferably comprised of a non-conductive, insulating material such as 
polyvinyl chloride (PVC). The electrodes 18a-18d may be attached to each 
of the support members 32a, 32b by conventional means such as masking 
tape, or may be inserted through aligned apertures within each of the 
support members for maintaining the electrodes in spaced relation. Each of 
the support members 32a, 32b is, in turn, positioned upon and supported by 
a pair of spaced storage tank brace bars 34a and 34b. Each of the brace 
bars 34a, 34b is provided with a generally inverted V-shaped upper portion 
upon which the support members 32b and 32a rest as particularly shown in 
FIG. 2. The combination of the brace bars 34a, 34b and support members 
32a, 32b maintains the four electrodes 18a-18d approximately one foot 
above the storage tank bottom 14e. Also positioned in a lower portion of 
the storage tank 14 is a discharge auger 36 for off-loading grain stored 
in the storage tank. The discharge auger 36 extends through an aperture in 
a wall of the storage tank 14 and is positioned generally along a 
centerline of the storage tank and immediately below the four electrodes 
18a-18d. The electrodes 18a-18d are preferably positioned approximately 12 
inches above the discharge gauge 36 in a typical installation. 
As shown in FIG. 1, adjacent ends of the first and third electrodes 18a and 
18c are coupled by means of an electrical lead 38a. Similarly, adjacent 
ends of the second and fourth electrodes 18b and 18d are coupled by 
another electrical lead 38b. The first pair of electrical leads 38a and 
38b thus connect alternately spaced electrodes to form a pair of spaced 
sensors each comprised of two electrode sections within the combine 
storage tank 14. When corn is deposited in the storage tank 14, the 
electrodes are completely covered and encompassed by the corn as shown in 
FIG. 2 for measuring the electrical conductivity of the corn between 
spaced, adjacent electrodes as described below. 
An opposed end of the third electrode 18c is coupled to a second terminal 
62b of the moisture tester 56 by means of the combination of an electrical 
lead 54a and a second jumper 64b. Similarly, an opposed end of the fourth 
electrode 18d is coupled to a first terminal 62a of moisture tester 56 by 
means of the combination of another electrical lead 54b and a first jumper 
64a. As shown in the figure, the first terminal 62a is designated 
"positive" while the second terminal 62b is designated "negative." The 
second pair of electrical leads 54a, 54b are easily connected and 
disconnected respectively from the first and second jumpers 64a, 64b by 
conventional means such as a plug-like or clip-like connector. Each of the 
jumpers 64a, 64b may be either hard wired or coupled to a respective one 
of the terminals 62a, 62b in a removable manner. The moisture tester 56 
applies a voltage across its first and second terminals 62a, 62b causing a 
current to flow within each pair of coupled electrodes. The moisture 
tester 56 then measures the current passing through the corn disposed 
between adjacent electrodes in the storage tank 14 to determine the 
moisture content of the corn in terms of its conductivity. 
Referring now to FIGS. 3, 4 and 5 there is shown a preferred embodiment of 
the corn moisture tester for use in the present invention, generally 
indicated by reference numeral 11. The corn moisture tester 11 is 
disclosed and claimed in aforementioned U.S. Pat. No. 4,954,783, issued 
Sep. 4, 1990, to the present inventor, the disclosure of which is 
incorporated in the present application by reference. The corn moisture 
tester 11 comprises a moisture meter 20, adapted for measuring the 
moisture content of corn or other vegetable matter, and a fixture 30 which 
includes a cradle 40, a pair of conductor blades 50, and a bracket 60 for 
mounting the cradle 40 to the housing 21 of the meter 20 so that the meter 
housing also acts as a handle when the moisture tester is removed from a 
combine for testing the moisture content of kernels on an ear of corn. 
The moisture meter 20 may be a commercially available instrument supplied 
by Delmhorst Instrument Company of Towaco, N.J. The unit 20 is described 
as a DHM-1 hay moisture meter and functions upon the principal that the 
electrical resistance of vegetable matter is a function of the moisture 
content of the vegetable matter. Accordingly, the moisture meter includes 
an electrical circuit for applying a predetermined voltage between a pair 
of terminals 22 (FIG. 5). The moisture tester 20 includes a switch 24, 
mounted to the handle 21, which, when actuated, applies a voltage across 
the terminals 22. Conductor blades 50 are mounted in the cradle 40 and 
electrically connected respectively to terminals 22. 
Thus, if vegetable matter, such as corn kernels, is placed between and in 
electrical communication with conductor blades or electrodes 50, the 
voltage across terminals 22 will cause current to flow therebetween, 
through the vegetable matter. The magnitude of the current is a measure of 
the resistance of the vegetable matter, and it gives, when displayed on 
meter 26, a quantitative measure of the moisture content of the matter. 
Meter 26 is illustrated in the form of a digital readout which displays a 
visual indication illustrated at 28 which is calibrated to indicate 
moisture percentage, rather than current, which the meter actually 
measures. The signal is, therefore, a useful quantitative representation 
of the moisture content of the vegetable matter. 
While most moisture meters measure electrical resistance between a pair of 
fixed points, other circuit means may be employed to measure other 
moisture-dependent properties of corn. 
As seen in FIGS. 4 and 5 the electrode blades 50 preferably are flat, thin 
blades, similar to conventional knife blades used for crafts and hobbies, 
including a sharp point 51 and knife edges 52 in the form of a chevron 
when viewed from the side, but honed to a sharp cutting edge. Preferably, 
the base of each blade 50 (i.e., the portion other than the honed edges) 
is covered with an electrically non-conducting material or coating so that 
only the chevron-shaped cutting edge is in electrical contact with the 
endosperm when the electrodes are embedded in the kernels. Thus, the 
cutting edges are the only active portions of the electrodes. An 
alternative electrode construction is an electrode in the form of a needle 
having a sharpened point providing the active area of the electrode, and 
the remainder of the needle being coated with an insulating material. The 
blade shape is preferred over the needle because it insures that at least 
one row of kernels will be pierced; whereas with a needle, the needle may 
be placed in an interstice between kernels, requiring replacement before a 
reading can be taken. 
By way of example, for the chevron blade electrode illustrated, the width 
of the active area may be about one-eighth of an inch, and the base of 
each electrode is covered with an insulating coating for a distance of at 
least three-eighths of an inch from the inner surface of the cradle. The 
electrodes 50 are adapted for piercing the pericarp of a kernel of corn 
and establishing electrical continuity with the endosperm thereof over a 
substantial area. The electrodes 50 are fixedly mounted to the terminals 
22 of the moisture tester 20 by soldering and the terminals may be mounted 
to the cradle by suitable insulating potting compound. 
The ear cradle 40 includes a fixed cradle section 42 adapted to receive an 
ear of corn 100 as illustrated in FIGS. 3 and 5. The fixed cradle section 
42 is mounted to the handle 21. It has a substantially cylindrical 
configuration and thereby defines a longitudinal cradle axis 43. When an 
ear of corn 100 is received in the cradle section 42 the longitudinal axis 
102 of the ear of corn 100 and the longitudinal cradle axis 43 are 
substantially aligned. 
The cradle 40 also includes a moveable cradle section or cover 45 mounted 
to the fixed cradle section 42 by hinge means 46. The hinged cradle cover 
45 is opened to permit an ear of corn 100 to be received in the cradle 
means 40. Thereafter, closing the hinged cradle cover 45 forces the ear of 
corn 100 onto the piercing electrodes 51 causing each of the electrodes 51 
to each pierce at least one of the kernels on the ear of corn 100. The 
depth of penetration of the conductor blades 50 is limited by the ear of 
corn 100 abutting the interior surface of the fixed cradle section 42. 
Although the hinged cradle cover 45 is not necessary to obtain the desired 
measurements, it is helpful when holding the handle in one hand, to close 
the cover 45 with the other hand. This insures that the ear will contact 
the concave surface 42 of the fixed cradle portion and that, in turn, 
insures proper penetration depth of the active surfaces of the electrodes. 
The cradle 40 which may be fabricated from a section of rigid tubular 
insulating material is fixedly secured to the moisture meter 20 by 
mounting bracket 60, in the form of a short, U-shaped section of PVC 
channel glued to the cradle base 44. The mounting means 60 has holes 
formed therein. The terminals 22 include a threaded terminal stud (not 
shown) that is passed through the holes. A threaded terminal cap 25, 
screwed over the studs, secures the cradle means 40 to the moisture meter 
20. 
FIG. 5 shows that the terminals 22, and the conductor blades 50 affixed 
thereto, pass through an opening 47 formed in the cradle base 44. Thus, 
the conductor blades 50 are in fixed special relation to the interior 
cradle surface 42. 
It is considered important that the configuration and orientation of the 
conductor blades 50 relative to the interior surface of cradle section 42 
and cradle axis 43, insure that each conductor blade will pierce the 
pericarp and contact the endosperm of at least one kernel of corn, without 
contacting the cob, when the ear of corn is properly placed in the cradle 
42. 
FIG. 5 illustrates that the conductor blades 50 each define a blade plane 
oriented at a predetermined angle Z with respect to the cradle axis 43. 
Furthermore, the conductor blades 50 define a predetermined blade width 
B.sub.w. FIG. 4 shows that the conductor blades are in fixed relation with 
the interior cradle surface 42 projecting inwardly a predetermined height 
B.sub.h above the surface 42. 
To prevent the conductor blades 50 from piercing the cob the predetermined 
blade height B.sub.h should be less than the kernel height K.sub.h. For 
ear corn in the field, kernel moisture may vary widely from ear moisture 
depending on the state of maturity and the weather. 
It should be noted that the configuration and orientation of the conductor 
blades 50 with respect to the cradle axis 43 insures that when an ear of 
corn 100 engages the concave inner surface of the fixed cradle section 42, 
each of the electrodes 50 bridges at least two rows of kernels and 
straddles at least two adjacent kernels. Thus, each conductor blade 50 
penetrates the pericarp and contacts the endosperm of at least one of the 
kernels on the cob 100. Because the active surfaces of the electrodes 50 
project inwardly a predetermined distance from the surface of cradle 
section 42, the blades 50 penetrate the corn kernels 106 without 
penetrating the underlying cob. Thus, as the moisture meter 20 applies a 
constant voltage across terminals 22, only the electrical resistance of 
the corn kernels, and not the cob nor the husk, is measured. 
To insure that each electrode blade 50 bridges at least two rows of kernels 
and straddles at least two adjacent kernels, the predetermined blade width 
B.sub.w and predetermined blade angle Z are chosen accordingly. Thus, the 
component of blade width, B.sub.w, which projects in a direction 
substantially parallel to the cob axis 102, must be greater than the 
thickness K.sub.t of at least one kernel. Likewise, that component of 
blade width which projects in a direction substantially normal to the cob 
axis must be greater than the width of at least one kernel. The plane of 
each electrode blade 50 forms an angle of approximately 45.degree. with 
the axis 102 of a corn cob received in the fixed cradle section 42. 
FIG. 4 shows that the cradle means 40 may include an optional cradle liner 
48 for use when testing the moisture of husked ears. The liner 48 provides 
a new interior cradle surface 42A which changes the depth of penetration 
of the blades. The cradle liner or spacer 48 is removable and has a 
thickness approximately equal to the thickness of the husk on an ear of 
corn. Thus, moisture tester 11 can be used to measure the moisture of ears 
that have not been husked when the spacer is removed, and for husked corn 
when the spacer is inserted. 
Also as shown in FIGS. 4 and 5, jumper wires 66 and 67 are coupled to 
terminals 22 for electrically connecting the corn moisture tester 11 to 
the previously described bulk corn moisture testing arrangement disposed 
in the combine's grain storage tank. The jumper wires 66, 67 may be 
coupled to a respective terminal 22 by conventional means such as 
soldering. The distal end of each jumper wire 66, 67 is provided with 
conventional quick disconnect coupling means such as a snap acting or a 
plug-like connector to facilitate coupling to and decoupling from a 
respective electrical lead to the array of electrodes in the combine's 
storage tank as previously described. 
Moisture content differences in the total mass of harvested corn are 
typically measured during corn off-loading. During off-loading the 
discharge auger is periodically stopped, perhaps as many as five or six 
times during the emptying of the tank, and moisture readings are taken as 
the corn passes downward through the electrodes allowing several portions 
of the entire corn load to be accurately sampled. In this manner, the 
farmer can obtain a highly accurate reading of the average moisture 
content of each load of corn recovered by the combine. 
There has thus been shown a corn moisture testing arrangement which is 
adapted for testing the moisture content of corn in bulk form such as in 
the storage tank of a combine or the moisture content of individual corn 
kernels on an ear of corn. In a combine, the moisture testing arrangement 
includes an array of conductive electrodes disposed in a lower portion of 
the combine storage tank which are electrically coupled to a conventional 
moisture tester located in the combine's cab. The moisture tester provides 
a combine operator with a visual indication of corn moisture content which 
may be used to determine when the corn should be harvested or in providing 
an estimated dollar value of the corn crop prior to harvesting. The 
moisture tester is easily disconnected from the electrode array in the 
combine's storage tank and removed from the combine for testing the 
moisture content of kernels still on an ear of corn. The inventive corn 
moisture testing arrangement may thus be used either by a commercial 
farmer for determining corn moisture content in bulk form, or by corn seed 
growers for determining drying characteristics of new hybrid seeds under 
development. 
It will be appreciated that while the foregoing description of the corn 
moisture tester of the invention includes specific details as to elements 
such as a moisture tester, such details are for the purpose of 
illustrating the invention and not intended as a limitation of the scope 
thereof. Persons skilled in the art will be able to modify some of the 
structure which has been illustrated and to substitute equivalent elements 
for those disclosed while continuing to practice the principle of the 
invention; and it is, therefore, intended that all such modifications and 
substitutions be covered as they are embraced within the spirit and scope 
of the appended claims.