Eppley Standard Cells & Pyranometers

© Brooke Clarke 2014

Background
Standard Cell
Pyranometers
Thermo Electric MiniMite 31101
Patents
Related
Links

Background

Eppley started making standard voltage cells in 1917 through the 1990s.  In the 1960s they started making instrumentation for the measurement of solar irradiance and atmospheric irradiance and are still in that business.

Standard Cell

The Weston Cell (Wiki) was the first electrochemical (Wiki) voltage reference cell and was the standard definition of the Volt from 1911 to 1990.

The Eppley patents allowed for a cell that could be shipped rather than one that needed to be hand carried so that it always pointed up.  The chemical composition of the Eppley cell was more stable than the Weston Cell.

Using the HP 34401 in 6 digit mode and default 10 Meg Ohm input impedance it reads: 1.018367 Volts.
At 10 Gig Ohm input resistance it reads: 1.018447. It's 76 F inside and 91 F outside.
A short time later it's: 1.018451.

Eppley EPP 811381 Standard Cell in Box
Eppley EPP
                  811381 Standard Cell in Box
Raw Eppley EPP 811381 Standard Cell
E.M.F. 1.0192 (the 1.019 was printed on the card & 2 was hand written.
Raw Eppley
                  EPP 811381 Standard Cell

Pyranometers

I got interested in these after doing some research on the Campbell-Stokes Sunshine Recorder.  As it happens I already had the Eppley standard cell so put them both on this web page.

"A pyranometer (Wiki)  is a type of actinometer used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density (in watts per metre square) from a field of view of 180 degrees."
When narrow bands are measured the device may be called a Radiometer, like the Exotech 100AX.

Precision Pyranometer, Model PSP

This unit covers 285 to 2800 nanometers.
The output is 7.4 mv in direct afternoon sun (28 Apr 2014 39N, 123 W) and current of 2 micro amps. 
This is normal.  Email from factory:
"Model 2 or PSP Pyranometer #12250F3 was supplied without a calibration performed which is why there is nothing on the label.
If you assume 7 mV / cal / cm2 / min (or in SI Units = 10 uV / Wm-2) then you have

7.4/7 = 1.06 Langley per minute (1 Langley = 1 Cal / cm2)  or in SI Units 7.4/10*1000 = 740 Wm-2 (watts per meter squared)."

Photos

Fig 1
Eppley
                  Precision Pyranometer, Model PSP
Fig 2 PT02H-4P (?) connector on unit
Mating connector is ____tbd____
Eppley
                  Precision Pyranometer, Model PSP
Fig 3 Desiccant (Wiki) Window
Eppley
                  Precision Pyranometer, Model PSP
Fig 4 Top view
Eppley
                  Precision Pyranometer, Model PSP
Fig 5 Label
Type _?_ Model 2 s/n: 12205F-3
Horizontal Surface
This radiometer has been compared
with the Eppley group of reference
standards.  The derived value of the
constant for this instrument is:
____?___ millivolts/cal-cm^-2 Min&-1 (Int.)

Eppley
                  Precision Pyranometer, Model PSP
Fig 6





Thermo Electric MiniMite 31101

This was advertised on eBay as an Eppley item, but that's not the case, it's made by Thermo Electric.  It does however contain a standard cell.

It's intended for testing potentiometers (like the Leeds Northroup), measuring temperature of a type-K thermocouple (Wiki) in deg C or voltage in mV.
The reason it was for sale is probably that the internal "D" battery had leaked and there was corrosion on the battery holder.
I have made a pdf version of the manual including bookmarks and color photos for the MiniMite and MultiMite, ask if you want to buy a copy.

Setup

Cleaned battery holder contacts.
Turned switch from Transit Lock to Operate and used (-) screwdriver to zero meter.
Held switch in Operate and turned Std Adj to zero meter.
So it should be ready to measure either mV or a type-K thermocouple as selected by the Range switch.
With a paperclip shorting the + and - inputs, in Operate Mode, when the scale wheel at the bottom is adjusted so the meter reads zero the mV scale reads zero (it does not matter which range you use).

Fig 1
Thermo
                  Electric MiniMite 31101
Fig 2
Thermo
                  Electric MiniMite 31101
Fig 3 The standard cell is in the diagonal holder.
Thermo
                  Electric MiniMite 31101




Patents


  494827 Voltaic cell, Edward Weston Newark, NJ, Nov 24, 1891, 429/125 ; 204/408; 429/222
1081365 Thermopile, William W Coblentz (licensed to Eppley), Oct 28, 1913, 136/213 - the basis of the Eppley Laboratory Thermopiles and probably the PSP
2613234 Plug or septum for electrolytic cells, Eppley Marion, Eppley Lab Inc, Nov 19, 1949, 429/125, 429/185
2816946 Cadmium standard cell, George D Vincent, Eppley Lab Inc, Jul 20, 1956, 429/125, 429/185

Related

Campbell Stokes Sunshine Recorder
Cloud Sensors
Dent Meridian Instrument - Dipleidscope
Digital Photography 204: Studio Flash - triggers SkyScan like lightening
Heathkit ID-4001 Weather Station
Oregon Scientific BAR122HGLA indoor WWVB clock, barometer, temperature, humidity & THGN321ES outdoor temperature and humidity.
IR Cloud Sensor
Seismometer & Geophone
Sensors - extensive page with many sensor types
SkyScan Severe Thunderstorm Detector
Soil Moisture Instruments
Sundial Sundials
SD_Pat2 Sundial Patents
TMQ-34 Meteorological Measuring Set -
Weather

TM 750-5-3 lists the GVH-1 Solar Radation Measuring Set.

Links

Standard Cells, Their Construction, Maintenance, and Characteristics by Walter J. Hamer, National Bureau of Standards Monograph 84, January 15, 1965.

PRC68, Alphanumeric index to web pages, Products for Sale, Contact
Page created 25 April 2014