Another from my collection the Metrotech 810, this one courtesy of Marg Straka from APA Gas.
The creator of the legendary Metrotech 810 locator, Earl Peterman, could not have imagined the impact that his creation would have on our utility locating industry. The US Patent that was lodged on the 31st of July 1980 (which was a Thursday) claimed that he had developed an “Apparatus For Determining the Distance to a Concealed Conductive Object Which Is Radiating an Alternating Current Signal,”
The abstract on the patent application reads as follows and is followed by 13 pages of descriptions, drawings and Patent Citations:
An apparatus to measure the distance to a concealed conductive object, radiating an electromagnetic signal, has two sensors, each adapted to receive the signal and to produce an output voltage proportional to the amount of signal received. Amplifier means amplify the output voltage. Automatic gain control means automatically controls the gain to the amplifier means such that the gain of the amplification of one of the output voltages is the same as the gain of the amplification of the other output voltage. Computing means calculate the distance based upon the two amplified output voltages. Display means display the calculated value.
Fortunately for us Peterman was able to see the need for a device that provided, clear and clean circular magnetic readings. With the advent of the Metrotech 810 Peterman introduced two industry breakthroughs which are still incorporated in today’s modern locators 39 plus years after the Patent was lodged.
The 810 was the first instrument that allowed the locator to analysis the magnetic field in both Peak and Null at the same time. This was achieved by the addition of extra antennae’s, orientated in the same direction as the normal peak antennae, which worked together to provide signal strength on the left and right sides of the locator, these reading activated the arrow response on the machines display. This “Digital Null response” proved more accurate than the previous “True Null” response.
The second breakthrough on the 810 was the machines ability to calculate a depth approximation for the buried utility, this was achieved by partnering the lower peak orientated antennae with one that is located higher up the locator’s body. The depth of the buried utility could now be calculated by the electronics comparing the signal strength of the lower antenna, the signal strength of the upper antenna and knowing the fixed separation between these two antennas.
To, view the full patent information click here: https://patents.google.com/patent/US4387340A/en?inventor=Earl+Peterman&oq=Earl+Peterman
Whilst you can hear the words of the great man himself here: https://www.youtube.com/watch?v=d4BIxGmwIxg