GB1297156A - - Google Patents

Abstract

1297156 Moisture measuring CUSTOM SCIENTIFIC ELECTRONICS PTY Ltd 10 Nov 1969 [11 Nov 1968] 54845/69 Heading G1N The moisture content of pasture, e.g. grass, crops, is determined from a direct meter readout 14, 47 by the capacitance of a plurality of probes 12 combined in two groups and connected in the frequency determining circuit of a freerunning oscillator 40, the output of which is compared, in a mixer 42, with the output of a fixed frequency crystal oscillator 41. The resultant beat frequency is applied to an audiofrequency amplifier, a Schmitt trigger, a differentiator, an emitter follower, an integrator, and to a pair of diodes (60), (61), Fig.6 (not shown), which switch each half cycle to give a direct meter 47 read-out which has a non-linear scale. In a modification, Fig.7 (not shown), two measuring ranges are provided, depending upon the quantity of pasture, the output of the Schmitt being taken through either of two branches of the differentiator. The probes 12, Fig.3 (not shown), are mounted below a plastics platform 11 composed of three layers, connections between one group of probes being made by a conductor extending between two layers, and connections between the other group of probes between the other layer and the middle layer. Each probe is sealed and connections from each group of probes is made to the oscillator inside the meter box 13. The circuitary is provided with a switch 15 having OFF, BATTERY TEST, and READ positions, and a zeroreset switch 16. The platform 11 is provided with handles 33, 38. Thus by determining the moisture content of the pasture, the dry pasture yield may be determined for a known area of pasture.