10PV Surface Temperature Probe Revision: 10/11 C o p y r i g h t © 2 0 1 0 - 2 0 1 1 C a m p b e l l S c i e n t i f i c , I n c .
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110PV Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. General .........................................................................1 1.1 Specifications............................................................................................2 2. Accuracy.......................................................................3 3. Installation and Wiring .................................
110PV Table of Contents Figures 1-1. 2-1. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 3-1. 3-2. 3-3. 3-4. 6-1. 110PV Temperature Probe ..................................................................... 1 Steinhart-Hart Error................................................................................ 3 110PV measured with a 3-wire half bridge ............................................ 4 110PV measured with a CR1000 using a 4-wire half bridge .................
110PV Surface Temperature Probe 1. General The 110PV-L temperature probe uses a thermistor to measure temperature. The probe is designed for measuring the back of photovoltaic (PV) module temperature but also can be used to measure other surface temperatures. The 110PV-L is compatible with all Campbell Scientific dataloggers. The 110PV-L consists of a thermistor encased in an aluminum disk (see Figure 1-1). The aluminum disk protects the thermistor and promotes heat transfer from surfaces.
110PV Surface Temperature Probe The 110PV ships with: 1) Adhesive Backed 3 cm Cable Tie Mount 2) Cable Ties 8” UV Stabilized 3) Resource CD 1.1 Specifications Temperature Range: -40° to +135°C Survival Range: -50° to +140°C 110PV Temperature Uncertainty -40° to 70°C: ±0.2°C 71° to 105°C: ±0.5°C 106° to 135°C: ±1°C Time Constant (average): Test τ Still Air 252 seconds Surface 25 seconds Water Submersion Depth: 50 ft (21 psi) Linearization Error: Steinhart & Hart equation; maximum error is 0.0024°C at -40°C.
110PV Surface Temperature Probe 2. Accuracy The overall probe accuracy is a combination of the thermistor's interchangeability specification and the accuracy of the bridge resistor. The Steinhart-Hart equation used to calculate temperature has a negligible error (Figure 2-1). In a "worst case" the errors add to an accuracy of ±0.2°C over the range of -40° to 70°C; ±0.5°C over the range of 71°C to 105°C; and ±1°C from 106°C to 135°C.
110PV Surface Temperature Probe Uncertainty on the graphs below is symmetric about 0. FIGURE 2-2. 110PV measured with a 3-wire half bridge FIGURE 2-3.
0PV Surface Temperature Probe FIGURE 2-4. 110PV measured with a CR1000 showing effects of cable length when using a cable offset FIGURE 2-5.
110PV Surface Temperature Probe FIGURE 2-6. 110PV measured with a CR200(X) showing effects of cable length when a cable offset is used FIGURE 2-7.
110PV Surface Temperature Probe 3. Installation and Wiring 3.1 Placement on a Photovoltaic (PV) Module The 110PV should be centered on the back of the PV module (see Figure 3-1). If the module has several distinctive photocells (see Figure 3-2), the 110PV should also be centered on the back of a photocell. FIGURE 3-1. 110PV mounted to a PV module FIGURE 3-2. At left is a PV module with distinctive solar cells. At right is a PV module that does not have distinctive solar cells.
110PV Surface Temperature Probe 3.2 Mounting to a PV Module or Other Device For mounting the probe to the back of a PV module or another device, the 110PV comes with an adhesive mounting disc adhered to its flat surface. To mount the 110PV, remove the paper from the mounting disc and adhere it to the back of the PV module or other device; refer to Section 3.1 for proper placement on a PV module. The mounting disc must be adhered to a clean surface for its adhesive to function properly.
110PV Surface Temperature Probe FIGURE 3-4. 110PV’s strain relief label 3.4 Submersion The 110PV can be submerged to 50 ft. It must be adhered to a dry clean surface before submerging. The probe’s adhesive mounting disc is not intended for submersion. Therefore the 110PV must be mounted to the measurement surface via a user-supplied method that is compatible with submersion. 4. Wiring Connections to Campbell Scientific dataloggers are given in Table 4-1.
110PV Surface Temperature Probe TABLE 4-1.
110PV Surface Temperature Probe 5.1 CRBasic The CR200(X)-series dataloggers use the ExDelSe instruction to measure the 110PV (see example in Section 5.1.1.1). The ExDelSe instruction has the following syntax: ExDelSE( Dest, Reps, SEChan, ExChan, ExmV, Delay, Mult, Offset ) The CR800, CR850, CR1000, CR3000, CR5000, and CR9000(X) can use either the BrHalf4W instruction or BrHalf instruction to measure the 110PV (see examples in Sections 5.1.1.2 and 5.1.1.3).
110PV Surface Temperature Probe 5.1.1.1 Sample Program for CR200(X) Series Datalogger 'CR200 Series Datalogger 'This example program measures a single 110PV-L probe 'once a second using the ExDelSE instruction and stores 'the average temperature in degrees C every 10 minutes.
110PV Surface Temperature Probe 'Convert Celsius to Fahrenheit T110PV_Temp_F = T110PV_Temp_C * 1.8 + 32 'Call AvgTemp data table CallTable AvgTemp NextScan EndProg 5.1.1.2 Sample Half Bridge Program for CR1000 Datalogger 'CR1000 Series Datalogger 'This example program measures a single 110PV-L probe utilizing 'the BrHalf instruction once a second and stores the average 'temperature in degrees C every 10 minutes.
110PV Surface Temperature Probe BeginProg Scan (1,Sec,3,0) ' Measure 110PV-L probe BrHalf (T110PV_mV,1,mV2500,1,Vx1,1,2500,True ,0,_60Hz,1.0,0) ' Convert mV to ohms T110PV_Res=4990*(1-T110PV_mV)/T110PV_mV ' Subtract off cable resistance (see 110PV-L cable for R_cable) T110PV_Res= T110PV_Res-R_cable ' Using the Steinhart-Hart equation to convert resistance to temperature T110PV_Temp_C = (1/(A+B*LOG(T110PV_Res)+C*(LOG(T110PV_Res))^3))-273.15 'Convert Celsius to Fahrenheit T110PV_Temp_F = T110PV_Temp_C * 1.
110PV Surface Temperature Probe 'Define a data table for 10 minute averages DataTable (AvgTemp,1,1000) DataInterval (0,10,Min,10) Average (1,T110PV_Temp_C,FP2,False) EndTable BeginProg Scan (1,Sec,3,0) ' Measure 110PV-L probe BrHalf4W (T110PV_mV,1,mV2500,mV2500,1,Vx1,1,2500,True,True,0,_60Hz,1.0,0) ' Convert mV to ohms T110PV_Res=4990 *T110PV_mV ' Use the Steinhart-Hart equation to convert resistance to temperature T110PV_Temp_C = (1/(A+B*LOG(T110PV_Res)+C*(LOG(T110PV_Res))^3))-273.
110PV Surface Temperature Probe Example Program for CR10X ;{CR10X} ;This program measures a single 110PV-L probe utilizing the ;P5 instruction once a second and stores the average ;temperature in degrees C every ten minutes. *Table 1 Program 01: 1 Execution Interval (seconds) ;Measure 110PV-L Probe 1: AC Half Bridge (P5) 1: 1 Reps 2: 25 2500 mV 60 Hz Rejection Range 3: 1 SE Channel 4: 1 Excite all reps w/Exchan 1 5: 2500 mV Excitation 6: 1 Loc [ V_Vx ] 7: 1.0 Multiplier 8: 0.
110PV Surface Temperature Probe ;Every ten minutes set output flag high to write data final storage 7: If time is (P92) 1: 0000 Minutes (Seconds --) into a 2: 10 Interval (same units as above) 3: 10 Set Output Flag High (Flag 0) ;Time stamp data record 8: Real Time (P77)^20972 1: 110 Day,Hour/Minute (midnight = 0000) ;Write 110PV-L 10 minute average to final storage 9: Average (P71)^4293 1: 1 Reps 2: 6 Loc [ Temp_C ] *Table 2 Program 02: 0.
110PV Surface Temperature Probe 6. Measurement Understanding the details in this section is not necessary for general operation of the 110PV Probe with CSI's dataloggers. Volt Excite BLACK GREEN Sense + Sense Signal WHITE RED Signal Reference PURPLE Signal Reference BLUE G THERMISTOR 4.99 k Ω, 0.1% CLEAR (shield) FIGURE 6-1.
110PV Surface Temperature Probe 7. Maintenance, Removal, and Calibration 7.1 Maintenance The 110PV probe requires minimal maintenance. Periodically check cabling for proper connections, signs of damage, and possible moisture intrusion. 7.2 Removal from Measurement Surface Remove the 110PV from the measurement surface by heating the probe to 70° to 80°C, and then pulling it off. CAUTION Prying the 110PV off without heating it will likely damage both the probe and PV module. 7.
110PV Surface Temperature Probe Symptom: Unstable Temperature Try using the 60 or 50 Hz integration options, and/or increasing the settling time as described in Sections 8 and 9. Make sure the clear shield wire is connected to datalogger ground, and the datalogger is properly grounded.
Appendix A. Probe Material Properties The probe consists of 6061 aluminum (clear anodized), thermistor, 3M9485PC adhesive, and Santoprene jacketed cable. A.1 3M 9485PC Adhesive Humidity Resistance: High humidity has a minimal effect on adhesive performance. Bond strengths are generally higher after exposure for 7 days at 90°F (32°C) and 90% relative humidity. U.V. Resistance: When properly applied, nameplates and decorative trim parts are not adversely affected by outdoor exposure.
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