WERC's historic PIR measurements

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 EKY Notes:

In July 2017 We reinstalled the radiometers at UKmet and Imn Met. I had them sent back to Eppley for recalibration/repair. I had Rob make up some new cables for the radiometers in 2016. They were wired incorrectly, and nothing seemed to be working right. He had them wired to correct for "Dome Temperature" (optional) instead of "Case Temperature" (required). He originally made them for case temperature, but had Allen rewire them for the dome temperature adjustment. Nothing was working properly. Allen and I made new cables in 2017 and wired them properly, things worked.

Anyway, it might just be some confusion between the terminology of Dome and Case temperature. Old PIRs didn't even have dome temperature, including some of our older models. 

 Recent Email Correspondence about dome vs case temperature

The cables that we took up were correct and I had Allen change them. My fault. rob

On Thu, May 25, 2017 at 7:23 PM, Emily Youcha <ekyoucha@alaska.edu> wrote:

Who said to do that?

On Thu, May 25, 2017 at 7:05 PM, Robert Gieck <regieck@alaska.edu> wrote:

That's why the cable I made last year and we changed were wrong.... we moved them to the dome.. rob

On Thu, May 25, 2017 at 6:00 PM, Emily Youcha <ekyoucha@alaska.edu> wrote:

Yes, I am sure. Case temperature is required for the measurement according to everything I read and the campbell manual for the eppley pir. Dome temperature can be used also for a correction, but not required. I checked with Busey and he doesn't use dome temp at all. But we can wire it in also though and read more about it:

See description:

http://www.eppleylab.com/instrument-list/precision-infared-radiometer/ Model PIR

The Precision Infrared Radiometer, Pyrgeometer, is intended for unidirectional operation in the measurement, separately, of downwelling or upwelling longwave irradiance. Unlike instruments that measure the shortwave (short) irradiance, there is no official ISO/WMO classification of pyrgeometers which are designed to measure the longwave (infrared) irradiance from the sky. The PIR comprises the same wirewound thermopile detector and temperature compensation circuitry as found in the SPP pyranometers. This thermopile detector is used to measure the “net radiation” of the PIR and a case thermistor (YSI 44031) is used to determine the outgoing radiation from the case. A dome thermistor is also included if one wishes to measure the dome temperature as compared to the case temperature to make any “corrections” to the final result.

On Thu, May 25, 2017 at 5:10 PM, Robert Gieck <regieck@alaska.edu> wrote: Are you sure about the dome temperature. That is what you are comparing the surface temp to not the case temp....rob

On Thu, May 25, 2017 at 3:50 PM, Emily Youcha <ekyoucha@alaska.edu> wrote: That is a good idea to have a badge I suppose.

We have to remake the radiation cables, the case thermistor wasn't wired up (Pin D and E) for the PIRs. Needs case temperature (required) and dome temp (F and G) is optional, but we might as well include dome temp. I am going to order some more connectors and then make up a bunch and one of us will drive up for a 1 day trip sometime in early June I guess. 

 Older Email Correspondence where he mentions dome temperature

> On Aug 6, 2015, at 6:50 AM, Robert Gieck <regieck@alaska.edu> wrote:

The shortwave PSP should read between 800 W/m2 and close to 0.

The longwave PIR won't read out in W/m2 until we process the data for dome temperature. There are thermisters in the domes that we need to get the temperature from and then calculate the output. I will have to look at some old data and see. If we were already temperature compensated, the range would be high end 500 and low end 250 (lowest is clear cold sky and highest is warm ground heated int he sunlight. The raw data is going to show a difference between the dome and what it's facing. The biggest difference would be the upward facing dome I think. Since these are differential readings they could be negative and still be correct. If the dome were around 35 F and the sky -40 (clear cold night) It would read work out like this (the values are approximate from memory). To get the emitted radiation, you need to use degrees Kelvin and the Stephan Boltzman constant.

Upward facing (amosphereric radiation)

  • -325 (dome emmitted W/m2 calculated from temp)
  • 375 W/m2 what it might read raw
  • +150 (received from the sky) so this is what we are after, the radiation incoming from the sky.

Downward facing (terrestrial radiation) A hot surface like dry-dark soil on a sunny dat might read like this.

  • +800 measured raw
  • -325 dome
  • 475 W/m2 emmitted to space

I can give you one of my old spreadsheets to use so you don't have to set up all the correction stuff.

Rob 

 Potential PIR CR1000 Programming Mistakes (Ken) regarding dome temperature and the use of panel temperature in a thermocouple measurement

Upon reviewing an old program for FBmet I noticed the PIRs program was using "dome temperature" (ex: "TLW_dome" and "ALW_dome") and using the "panel Temperature" ? as the thermocouple reference. I Rob started using temperature adjustments but at a minimum Case temperature should have been used, which would have been a thermistor in the PIR, not a thermocouple (?where would the thermocouple be?).

    • public rad_mV(MUX1_QTY)
    • alias rad_mV(1) = TLW_mV
    • alias rad_mV(2) = ALW_mV
    • alias rad_mV(3) = ISW_mV
    • alias rad_mV(4) = RSW_mV
    • Alias rad_mV(5) = Net_rad
    • Public radiation(MUX1_QTY)
    • Units radiation() = wpm2
    • Alias radiation(1) = TLW
    • Alias radiation(2) = ALW
    • Alias radiation(3) = ISW
    • Alias radiation(4) = RSW
    • 'alias radiation(5) = Net
    • Public tc(2)
    • Units tc() = degC
    • 'Units tc(2) = degC
    • Alias tc(1) = TLW_dome
    • Alias tc(2) = ALW_dome
    • sub read_mux1()
    • MUX1 has 5 radiometers, 2 thermocouples, 1 pressure transducer,
    • and a 10:1 voltage divider
    • PortSet(MUX1_ENABLE_PORT, 1)
    • terrestrial long wave radiation
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • VoltDiff(TLW,1,mv25,MUX1_DE,1,0,250,TLW_MULT,0)
    • atmospheric long wave radiation
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • VoltDiff(ALW,1,mv25,MUX1_DE,1,0,250,ALW_MULT,0)
    • incident short wave radiation
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • VoltDiff(ISW,1,mv25,MUX1_DE,1,0,250,ISW_MULT,0)
    • reflected short wave radiation
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • VoltDiff(RSW,1,mv25,MUX1_DE,1,0,250,RSW_MULT,0)
    • net radiation
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • VoltDiff(Net_rad,1,mv25,NET_DE,True,0,250,1000/NET_MULT,0)
    • If WS_3m>=5 Then
    • Net_rad=Net_rad*(1+0.021286*(WS_3m-5))
    • Else
    • Net_rad=Net_rad
    • EndIf
    • IMPORTANT: thermocouple reference temperature is currently
    • set to use logger panel temp, but this assumes that the
    • multiplexer is in the same enclosure with the same temperature
    • environment and gradients.
    • measure radiometer thermocouples:
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • TCDiff (tc(1),1,mV2_5C,MUX1_DE,TypeT,panelT,1,0,250,1.0,0)
    • PulsePort(MUX_CLOCK_PORT ,MUX_CLOCK_PULSE)
    • TCDiff (tc(2),1,mV2_5C,MUX1_DE,TypeT,panelT,1,0,250,1.0,0)
    • PortSet(MUX1_ENABLE_PORT, 0)
    • EndSub ' read_mux1
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