Railroad car wheel bearing heat signal processing circuit

In a railroad hot box detector system of the type including infrared responsive scanner means associated with a sensing zone along a section of track adapted to scan bearings of a railroad car within said sensing zone and to generate an output voltage signal in response thereto having an amplitude and waveform indicative of the type of bearing being scanned and a sampling circuit adapted to sample the output of said scanner means into a preselected number of discrete samples the improvement comprising:

• means for establishing a threshold signal level related to the average of the discrete voltage levels;
• means for determining the number of discrete samples falling between the crossing points of said waveform through said threshold;
• means for obtaining a first predetermined portion of the samples falling between the crossing points;
• means for obtaining the sum of the voltage levels during said first predetermined portion;
• means for obtaining a second predetermined portion of the samples falling between the crossing points;
• means for obtaining the sum of the voltage levels during said second preselected portion, and,
• means for comparing said first and second sums to obtain information indicative of the type of bearing being scanned.

The method for eliminating spurious signals in the processing of a railroad car bearing heat signal waveform comprising the steps of:

• (a) scanning the bearings of a railroad car within a sensing zone along a length of track to generate a waveform indicative of the heat condition of the bearing being scanned;
• (b) sampling the output of said scanner into a preselected number of discrete samples;
• (c) adding the voltage levels of all the samples of said waveform in excess of zero and dividing the sum so obtained by the number of samples added to obtain a threshold;
• and
• (d) determining the points where the waveform would cross said threshold and eliminating all the sample points outside said crossing whereby to eliminate spurious signals.

The method for discriminating between waveforms generated by roller bearings and friction bearings in the processing of a railway car bearing heat signal waveform comprising the steps of:

• (a) scanning the bearings of a railroad car within a sensing zone along a length of track to generate a waveform indicative of the type of bearing being scanned;
• (b) sampling the output of said scanner into a preselected number of discrete samples;
• (c) adding the voltage levels of all the samples of said waveform in excess of zero and dividing the sum so obtained by the number of samples added to obtain a threshold;
• (d) determining the points where the waveform would cross said threshold and eliminating all the sample points outside said crossing;
• (e) determining the sum of the voltage levels of the samples of said waveform within a first portion of the threshold crossing points;
• (f) determining the sum of the voltage levels of a second portion of the samples of said waveform between the threshold crossing points;
• and,
• (g) obtaining the ratio of the sum of the first portion voltage levels to the sum of the voltage levels of the second portion whereby to obtain a number indicative of the type of bearing under investigation.