초록 ▼

The High Accuracy Electronic Material Level Sensor (electronic dipstick) is a sensor based on time domain reflectometry (TDR) of very short electrical pulses. Pulses are propagated along a transmission line or guide wire that is partially immersed in the material being measured; a launcher plate is

The High Accuracy Electronic Material Level Sensor (electronic dipstick) is a sensor based on time domain reflectometry (TDR) of very short electrical pulses. Pulses are propagated along a transmission line or guide wire that is partially immersed in the material being measured; a launcher plate is positioned at the beginning of the guide wire. Reflected pulses are produced at the material interface due to the change in dielectric constant. The time difference of the reflections at the launcher plate and at the material interface are used to determine the material level. Improved performance is obtained by the incorporation of: 1) a high accuracy time base that is referenced to a quartz crystal, 2) an ultrawideband directional sampler to allow operation without an interconnect cable between the electronics module and the guide wire, 3) constant fraction discriminators (CFDs) that allow accurate measurements regardless of material dielectric constants, and reduce or eliminate errors induced by triple-transit or “ghost”reflections on the interconnect cable. These improvements make the dipstick accurate to better than 0.1%.

대표청구항 ▼

Apparatus for measuring the level of a material, comprising: a precision time base for generating a real time transmit pulse and a gate pulse; a directional sampler having a first port for receiving the real time transmit pulse, a second port coupled to the first port for transmitting the real time

Apparatus for measuring the level of a material, comprising: a precision time base for generating a real time transmit pulse and a gate pulse; a directional sampler having a first port for receiving the real time transmit pulse, a second port coupled to the first port for transmitting the real time transmit pulse, a third port coupled to the first port and isolated from the second port, and a fourth port coupled to the second port, the directional sampler being gated by the gate pulse; a dipstick assembly connected to the second port; first and second constant fraction discriminators (CFDs) of opposite polarity, the first CFD switchingly connected to the third and fourth ports, the second CFD connected to the fourth port a set-reset flip-flop connected to the first and second CFDs.