Workshop 2 Data-Logger Principles

Transcription

1 1 The University f British Clumbia GEOG 309 / Andreas Christen February 7, 2008 Wrkshp 2 Data-Lgger Principles Gals 1 Becme familiar with a digital data-lgger. 2 Prgram the data-lgger and recrd a signal f a sample sensr (thermcuple). 3 Dwnlad the recrded data t a cmputer. In grups f 3 t 4 students yu will be prvided with a data-lgger Campbell Scientific 21 X, a 12V battery, battery-cnnectin cables (a red and black cable including a white plug and a fuse), and a small piece f thermcuple wire. A data-lgger (als: lgger) is a prgrammable multi-meter with the ability t trigger measurements at specific times and stre this data in a memry. All data will be time-stamped with the exact measurement time. Typically, we (1) prgram a lgger in the lab, (2) cnnect sensrs t the lgger, (3) test the prgram and sensrs thrughly in the lab, (4) install and run the lgger at a field site, (5) check the lgger regularly and (6 cllect the data (n a memry mdule, a printer r n a cmputer). Our sample lgger A Campbell Scientific 21X - has a numeric keybard fr cntrlling and prgramming, a 8-digit display t check values and get feedback frm the lgger, a serial input-utput (9-pin plug) t cnnect the lgger t a cmputer and dwnlad data etc., and 2 x 24 cnnectin terminals in tw strips, where yu can cnnect varius sensrs and the battery. Let us start right away and pwer-up the lgger! Be aware that lse cables may create a shrtcut and destry the battery r lgger! The red cable is equipped with a fuse that will blw in case yu accidentally create a majr shrtcut but it cannt prevent all damage.

2 2 Cnnect the red cable that includes the fuse t the terminal labeled 12V n the right f the lwer strip f the 21X, and the black cable t the rightmst terminal n the lwer strip labeled. Be sure yu screw the cables tightly int the terminals 1. Nw, cnnect the white plug t the battery. If yu cmpleted this task the lgger will start-up and say Hell t yu! 1 Pwer and battery Batteries can discharge. Even if the battery s vltage seems rather cnstant, the capacity f a battery t stre energy is limited. When the battery is clse t empty, vltage will drp, the lgger will eventually shut dwn and yu might lse all yur data and prgrams! In yur field wrk it is essential t calculate hw lng yur battery will pwer safely yur set-up in advance and cntinuusly mnitr the battery s vltage. Our batteries shuld never drp belw 11V therwise they experience irreversible damage. The capacity f a battery is usually expressed in Ah - ampere-hurs - a cmmn measure f hw lng the battery will last when fully charged (and brand-new) and a cntinuus current is drained. After many recharge cycles and by aging f the battery, the capacity usually decays. Hw many Ah is yur battery suppsed t have? Hw lng shuld it pwer the lgger, when the lgger typically drains 25mA? 1 Sme lggers have als an internal battery, but we will nt use it. S please d nt use the metallic switch n the right lwer side f yur lgger (if there is any).

3 3 2 Prgrams, instructins and parameters A lgger can be prgrammed t d specific instructins in a defined sequence. A lgger prgram is a timetable (a sequence) f ne r several instructins that are subsequently carried ut (see figure, right). Instructins are basic tasks, such as measuring a sensr, averaging data r write data in the final memry. They can be cmbined in nearly any rder. There are fur classes f instructins n this lgger (see table belw). Instructins can have ne r several parameters. If yur instructin is a vltage measurement these parameters will define where (terminal) and hw (the vltage range) we wuld like t d the measurement. All instructins are summarized in the prmpt sheet at the end f this hand-ut. Task Instructin class Instr. # Measure sensr signals (vltages, resistances, thermcuples, clcks, digital sensrs etc.) and stre values in the lgger s input strage. Perfrm numerical calculatins in the input strage, e.g. divide ne value by anther. Mve r average the values in the input strage int a final strage, i.e. stre an average ver 10 minutes f all measurements in the input strage. Lgic decisins (If.. then.. else), lps, flags. Input instructins 1-26 Prcessing instructins Output prcessing instructins Prgram cntrl instructins Yu see, we have tw types f memries, an input strage and a final strage. What is their difference?

4 4 Summary f imprtant mdes (see text). Mde Use Keybard Access 0 Lgger-mde Cmpile and run prgrams 1 Prgramming-mde Write and mdify prgrams 5 Clck-mde Check and set clck 6 Input-strage-mde Display input strage lcatins

5 5 3 Set the lgger s time and date T get used t the keybard navigatin let us set the lgger s clck. The lgger has different perating mdes - ne is the clck-set mde (mde 5). All mdes have numbers and are accessed by first entering the -key n the keybard fllwed by the mde number (see table n page 4). First, let us check if the lgger is prperly running. T enter the lgger-mde (mde 0) press then. The lgger displays LOG. Next, let us g t the clck-mde (mde 5), press then n the keybard t display current time. Yu will get smething like :00:11:23. This is the time since yu cnnected the battery earlier tday in HH:MM:SS. Every time yu discnnect pwer the clck will be reset, and yu must reenter time and date (and prgrams). Nw, press (fr advance) t prceed t the year display. Enter a tw-digit year, e.g. press fr Press t cnfirm and advance t the Julian day display. The Julian day is the day f the year starting at January 1 st :

6 6 Determine tday s Julian day, enter the value and press t cnfirm and advance t the hurs-minutes display. In the hurs-minutes-display enter the current 24-h time in 4 digits withut :, e.g. fr 4:35 pm. Press t cnfirm and precisely start the clck. Well dne! Yu see, the lgger has a quite ld-fashined user-interface - N bright LCD tuch-screens, n clr graphics. As lng as yu d nt discnnect pwer, this clck will run frever. Whenever yu press yu can check the clck. Press t return t the lgger-mde. If yu will use a lgger in the field-camp, yu shuld check and adjust yur clck regularly. 4 My first prgram step by step Let us measure an internal temperature f the lgger and then the battery s vltage. T write a new prgram, we enter the prgramming-mde (mde 1) by pressing. Press t advance t the prgram s executin interval. The executin interval defines hw frequently the prgram will run in a lp - in secnds. Valid entries are t 6553 secnds. Let us measure temperature and battery every secnd, s press, then. The prgram will run every secnd. Next, we are prmpted t insert a specific instructin that measures smething. The fllwing table summarizes the mst imprtant input instructins. A cmplete list f all available input instructins can be fund n the lgger s prmpt sheet. A simple example is the panel temperature f the lgger (the internal reference temperature fr thermcuple measurements). We see the panel temperature can be measured by instructin 17. There is a thermistr inside the lgger and this thermistr is pre-wired. S, instructin 17 des nt require wiring anything

7 7 t the terminal strips. Yu lgger displays 01:P00 and yu are ready t insert instructin 17, s press fllwed by. The lgger asks yu t enter a parameter 1 ( 01:0000 ). Instructin 17 has ne parameter nly, called LOC (see table). LOC is the input lcatin in the memry where yu wish t intermediately stre the measured panel temperature. Let us stre it at lcatin 1, s enter then Tip: memrize r write dwn the input lcatins (numbers and what is measured) - we will later refer t them. The display shws 02:P00 and we are ready t enter a new, secnd instructin. Lk up the table fr an instructin that measures battery vltage. Enter its number and then t insert the instructin. Again, there is n need t wire anything t the terminal strips, because the battery is already cnnected. Similarly, this instructin has ne parameter the input lcatin. Let us stre the battery vltage at the next free input lcatin, 2, s enter then. Memrize, panel temperature is in input lcatin 1, battery vltage in input lcatin 2. When a prgram is first entered, r if any changes are made in the prgramming-mde, then the prgram must be cmpiled. Press t cmpile yur prgram and t return t the lgger-mde. The display shws LOG1. Cngratulatins, yur first lgger prgram runs! Right nw, yur lgger measures panel temperature and battery vltage every secnd and writes these values int input lcatins 1 and 2. But hw can we access these values? Again, let s g smewhere else, in a new wrld, in the input-strage-mde (mde 6). Mde 6 is where yu can display all assigned input lcatins. Press. Press t advance t the first lcatin - the panel temperature, read yur lgger s temperature.

8 8 Press t advance t the next, the secnd lcatin the battery vltage. Yu can press (back) t g back t the first lcatin. Yu can brwse thrugh all input lcatins. Lcatins 3 and higher will be empty and display We have nt assigned any measurements, yet. Panel Temperature: Battery Vltage: 5 Thermcuple prgram 2. Our secnd example is mre representative f a data cllectin situatin. This time the panel temperature will be used as the reference temperature fr a cppercnstantan thermcuple (TC). Thermcuples measure the temperature relative t their reference junctin temperature. T btain the abslute temperature, the reference junctin temperature must be knwn. S let us extend the first prgram, press t enter the prgramming mde and tw times t skip ver the first instructin 1 (panel temperature 17) and 2 (battery vltage 10) and advance t the 3 rd empty instructin. Yu will see 03:P00. We will use a thermcuple and wire it t channel 1 in the upper terminal strip. S use the thermcuple wire and cnstruct ne half f the thermcuple (1 junctin with tw wires, see figure). The ther half, i.e. the cld junctin, is inside the lgger and mnitred with the abve panel temperature. The cpper lead (Cu, blue shield) must be cnnected t the leftmst high input (1H) and the cnstantan lead (C, red shield) must be cnnected t the next lw 2 This example is taken frm the 21X Datalgger manual by Campbell Scientific Ltd.

9 9 input (1L). We'll read the sensr every secnds, and later stre average values every minute. Let us check n the prmpt sheet, hw t measure TCs: We see, Instructin 14 measures TC temperature with a differential vltage measurement. S enter and t insert instructin 14. Oh, this instructin has 8 parameters! The display prmpts fr parameter 1 ( 01:00 ). This is REPS, the number f times t repeat the measurement. There is nly ne thermcuple, s we enter and advance with. If there were several TCs (e.g. in a sil temperature prfile) they culd be wired t sequential input channels (1,2,3, ) and the number f TCs wuld be entered in Parameter 1. The lgger wuld measure all f the TCs in this single instructin. Parameter 2 (display 02:00 ) is called RANGE. This is the full-scale vltage input range (see table right) t use when making the measurement. TC signals are very small (remember: 41µV K -1 difference in temperature between the measurement and reference junctin fr Cu-C). If we use a range cde f (± 5 mv full scale, slw integratin), the TC vltage will nt exceed the input range as lng as the measurement junctin is within 1250ºC f the panel temperature. That s far enugh! Parameter 3 (display 03:00 ) IN CHAN specifies the input terminal n which t make the measurement. We chse, because we wire the TC t 1H and 1L. Parameter 4 (display 04:00 ) TC TYPE specifies the type f the thermcuple: Chse the type s number and press

10 10 Parameter 5 (display 05:00 ) REF LOC specifies the Input Strage lcatin in which t find the panel temperature. Lk up yur ntes t see where we stred the panel temperature? Enter the input strage lcatin f the panel temperature and press. Parameter 6 (display 06:00 ) REF specifies the Input Strage lcatin where we stre the calculated thermcuple temperature. The next free lcatin is and press. Add this t yur ntes fr reference. Parameters 7 and 8 are the multiplier and ffset which cnvert the measurement t engineering units. The TC instructins return the measurement in units f ºC when a multiplier f and an ffset f are used. The example was explained ne keystrke at a time. Instead f listing each keystrke, the fllwing table summarizes the whle instructin: Press t cmpile the prgram and t return t the lgger-mde. Hw can we check if ur thermcuple is crrectly wrking?

11 11 6 Final strage Hw t stre data? Right nw, values are measured and written int the input strage but in the next secnd verwritten by the next measurement. We must find a way t write data frm the input lcatins t the final strage fr dwnlading later. Fr this purpse, we use utput prcessing instructins: Again, we will extend the same prgram, s press t enter the prgramming mde and three times t skip ver the first three instructins. Yu will see 04:P00. Let us first enter a lgical functin - an if-functin - that writes values int the final strage if we reach a full minute. Press t enter instructin 92, If time is Parameter 1 is the timing within the interval. Because we have nly ne minute 3, we must enter. Parameter 2 is the length f the interval, we say 1 minute, s press. Parameter 3 asks what t d - we culd d many things (see prmpt sheet n last page) - but right nw we wuld like t utput the data, and this is dne by setting the s-called utput flag ( ). 3 If we wuld write 10-minute averages, we wuld fr example enter 01:5 and 02:10, s at 16:05, 16:15, 16:25, 16:35 data wuld be averaged ver the last 10 minutes and written int the final strage. Typically we say 01:00, 02:10 in rder t get values at 16:10, 16:25, 16:30,

12 12 We definitely must knw when the measurement was taken. Let us write a date/time-stamp int the final strage (Instructin 77, Real Time ). We enter. Instructin 77 has nly ne parameter. This parameter describes the frmat f the date/time-stamp. Enter the cde fr Julian day, hur-minute but n secnds and press. The display shws 06:P00. Finally, we calculate an average f all 60 measurements taken in the last minute and stre this average in the final strage (Instructin 71, Averaging ). We enter. This instructin has tw parameters (see table, previus page): Parameter 1 defines the number f repetitins. We wuld like t calculate 3 averages, namely average panel temperature, average battery vltage and average thermcuple temperature, s we have 3 repetitins. Parameter 2 is the first f the three input lcatin Press t cmpile the prgram and t return t the lgger-mde. Run the lgger fr sme minutes, and let us see in class hw we can dwnlad the values t a cmputer.

13 13 Yur prgram at a glance *Table 1 Prgram 01: 1 Executin Interval (secnds) 1: Panel Temperature (P17) 1: 1 Lc 2: Batt Vltage (P10) 1: 2 Lc 3: Thermcuple Temp (DIFF) (P14) 1: 1 Reps 2: 1 5 mv Slw Range 3: 1 DIFF Channel 4: 1 Type T (Cpper-Cnstantan) 5: 1 Ref Temp (Deg. C) Lc 6: 3 Lc 7: 1.0 Mult 8: 0.0 Offset 4: If time is (P92) 1: 0 Minutes int a 2: 1 Minute Interval 3: 10 Set Output Flag High 5: Real Time (P77) 1: 0110 Day,Hur/Minute (midnight = 0000) 6: Average (P71) 1: 3 Reps 2: 1 Lc

14 14 7 Reference: sample instructins fr cmmn climatlgy sensrs Fr mre examples see als the prgram Shrt Cut which can be dwnladed fr free frm Campbell Scientific s webpage ( 7.1 Pyranmeter The thermpile f the pyranmeter is creating a vltage strng enugh t be measured using a differential vltage instructin (2). Cnnect the tw wires t subsequent H and L inputs, e.g. 1H and 1L: Vlt (Diff) (P2) 1: 1 Reps 2: 1 15 mv Slw Range 3: 1 DIFF Channel [Adjust in yur prgram] 4: 1 Lc [Adjust in yur prgram] 5: 0.01 Mult [Adjust yur instrument s sensitivity] 6: 0.0 Offset 7.2 Infrared thermmeter (IRT) The Everest IRT prduces an utput vltage prprtinal t the measured radiative temperature in ºC. There is already an internal electrnic that calculates Stefan-Bltzmann s Law. Again, we can measure the IRT vltage using the differential vltage instructin (2), but this time with a different range. Cnnect the blue utput cable t any H, the white cable t a subsequent L, e.g. 8H, 8L. The sensr must be pwered. Cnnect the IRT black cable t any, the red cable t 12+. Vlt (Diff) (P2) 1: 1 Reps 2: mv Slw Range 3: 8 DIFF Channel [Adjust in yur prgram] 4: 1 Lc [Adjust in yur prgram] 5: 0.1 Mult 6: 0.0 Offset 7.3 Cup anemmeter A cup anemmeter creates electrmagnetic pulses while rtating. The number f pulses in a given time frame is prprtinal t the wind speed. We can cunt pulses using the instructin 3. Cnnect ne wire frm the cup anemmeter t the Pulse prt 1 in the lwer terminal strip and the secnd ne t. Similarly, we can measure rain gauges.

15 15 Pulse (P3) 1: 1 Reps 2: 1 Channel number [Adjust in yur prgram] 3: 2 Pulse cunt cde Switch Clsure 4: 1 Lc [Adjust in yur prgram] 5: 0.3 Mult [Adjust t cnvert pulses t m/s] 6: 0.0 Offset 7.4 Cmbined thermmeter / humidity prbe. The HMP 35 sensr gives yu an idea f a mre cmplex wiring. It can measure bth, air temperature and relative humidity and has seven cnnectin wires. The thermmeter is a standardized thermistr (107 Temperature), s let us send a defined current thrugh it and measure the vltage drp. Fr this purpse we will use the excitatin prts. Here we can - fr a shrt time and t cnserve energy send a well-defined current thrugh the thermistr. We use instructin 11 (Temp 107 Prbe) t measure the vltage drp and cnvert it t a temperature. This instructin returns temperature in ºC. Temp 107 Prbe (P11) 1: 1 Reps 2: 1 SE Channel [adjust] 3: 1 Excite Prt [adjust] 4: 1 Lc [adjust] 5: 1.0 Mult 6: 0.0 Offset The humidity sensr is recrded with excitatin and a single-ended vltage measurement (instructin 4). First, we pwer the sensr fr 150 millisecnds, then d the measurement and finally turn it ff again. The settings belw return the relative humidity in %. 6: Excite Delay Vlt (SE) (P4) 1: 1 Reps 2: mv Slw Range 3: 2 SE Channel [Adjust in yur prgram] 4: 2 Excite all reps w/exchan 3 [Adjust in yur prgram] 5: 15 Delay (0.01 sec units) 6: 5000 mv Excitatin 7: 2 Lc [Adjust in yur prgram] 8: 0.1 Mult 9: 0.0 Offset

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