1970s Hewlett-Packard HP 3810A Total Station

The HP 3810A Total Station, the first instrument bearing this name.
Figure 1: The HP 3810A Total Station, the first instrument bearing this name.
In May 2019 I received my first HP 3810A. That example had been through the wars and was in a terrible state. All plastic components (covers, instrument panel, knobs, ocular) were broken and so was the internal cast-metal frame. In addition most parts of the yoke were heavily corroded and the battery-compartment and box were missing.
Still I was happy to receive it as this instrument was the very first to bear the name "Total Station" (see figure 7), a term now commonly used for any geodetic instrument capable of measuring distances, reducing them to horizontal or vertical and storing these values together with the corresponding vertical and horizontal angles in memory.
Sadly enough this first example was that terrible state that I did not want to display it. This all changed in June 2020 when another HP 3810A surfaced on a Dutch online marketplace. That one was in much better state, most likely as it had always been stored in its original case (see figure 13). It also was slightly older (ser.no. 733 vs. 1159), but as a result of that it lacked the text "Total Station" on the front. Luckily that front section was the only part of the first one that I found to have survived its rough treatment. So I dismantled the broken one, took off the front plate (and a few other parts that survived) and mounted the front plate on the older version, while keeping the original one.


The HP 3810A Total Station from the other side.
Figure 2: The HP 3810A Total Station from the other side.
The HP 3810A was not yet a Total Station in the sense of its modern successors like the 1980 Wild TC1 and the 1999 Leica TCRA 1101. Although it "... measures slope distance, zenith angle, corrects for curvature and refraction, and computes and displays horizontal or vertical distance", there was no internal storage yet, nor was there a way to read the horizontal circle electronically (that would first be achieved in 1977 in their model HP 3820A1).
The HP 3810A was introduced in November 19752 and has been produced until at least 19813. It was based on their HP 3800A Distance Meter which was introduced in April 1970.4
Most likely the concentric lens of the EDM influenced Wild-Heerbrugg in their design of the TC1, the first total station to look and measure along the same optical axis.

Aiming device
The HP 3810A was originally constructed with an internal telescope. The battered one that I found still had this telescope, although the eyepiece is missing its original collar. The second one, which is shown here, had the original internal telescope replaced by an external and most likely more powerful one. The bracket for this external telescope is still present, but the scope itself sadly enough is missing. The internal telescope was taken out and replaced by a counterweight to balance out the new scope. I therefore kept all the parts of the original scope of the battered one in the hope that one day I can revert this HP 3810A to its original scope.


A close-up of the now generally used type-name Total Station.
Figure 3: A close-up of the now generally used type-name Total Station.
Specifications
The HP 3810A had a range of 1.6 kilometres using a set of three prisms.5 Its accuracy was stated as 5 millimetres + 5 millimetres per kilometre for a temperature range of -10°C to +40°C. It could do these measurements in single distance measuring mode or in tracking mode. In the mode the distance would be displayed in 3 decimal metres, otherwise in 1 decimal.
The horizontal circle could be read directly to 50 deci-milligon (20 arc-seconds) and estimated down to 10 deci-milligon (5 arc-seconds). The zenith angle was measured with an accuracy of about 90 deci-milligon or 30 arc-seconds.
With 12.1kg the instrument hardly was a light-weight instrument, while its dimensions of 345 x 360 x 325 millimetres makes it a substantial piece.


Notes

[1]: Denekamp, J., 'Een nieuwe generatie registrerende tachymeters', in: Nederlands Geodetisch Tijdschrift, 9e jaargang, no. 7, september 1979 (Delft, 1979), pp.107-119.
Cooper, M.A.R., Modern Theodolites and Levels, (Oxford, London, Edinburgh, Boston, Palo Alto, Melbourne, 1982), p.104.
[2]: 'New H.P. Instrument', in: The California Surveyor, Winter 1975, (Hayward, 1975), pp.20-21.
[3]: Advertisement in Geodesia: Nederlands Geodetisch Tijdschrift, 23e jaargang, no.3, maart 1981, (Apeldoorn, 1981), p.169.
[4]: Hewlett-Packard, Civil Engineering Products, (Loveland, 1979), p.3.
[5]: Hewlett-Packard, Civil Engineering Products, (Loveland, 1979), p.6.

If you have any questions and/or remarks please let me know.

The handlebar for carrying the instrument.
Figure 4: The handlebar for carrying the instrument.
 
The eyepiece for the horizontal circle is reminiscent of that introduced by Zeiss.
Figure 5: The eyepiece for the horizontal circle is reminiscent of that introduced by Zeiss.

A view at the horizontal circle, here reading 399.672 gon.
Figure 6: A view at the horizontal circle, here reading 399.672 gon.
 
The front with the concentric lenses, an idea later taken over by Wild for the TC1.
Figure 7: The front with the concentric lenses, an idea later taken over by Wild for the TC1.

The rear of the HP 3810A showing the controls and type-label.
Figure 8: The rear of the HP 3810A showing the controls and type-label.
 
A closer look at the rear of the HP 3810A.
Figure 9: A closer look at the rear of the HP 3810A.

The battery compartment of the HP 3810A sits under the body above the yoke and vial.
Figure 10: The battery compartment of the HP 3810A sits under the body above the yoke and vial.
 
The battery compartment now is empty..
Figure 11: The battery compartment now is empty..

The switches for changing between metres and feet and between gon and degrees.
Figure 12: The switches for changing between metres and feet and between gon and degrees.
 
The carrying case of the HP 3810A.
Figure 13: The carrying case of the HP 3810A.

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