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INSTRUCTION MANUAL

247 Conductivity and

Temperature Probes

Revision: 3/96

C o p y r i g h t   ( c )   1 9 9 4 - 1 9 9 6

C a m p b e l l   S c i e n t i f i c ,   I n c .

Summary of Contents for 247

Page 1: ...INSTRUCTION MANUAL 247 Conductivity and Temperature Probes Revision 3 96 C o p y r i g h t c 1 9 9 4 1 9 9 6 C a m p b e l l S c i e n t i f i c I n c ...

Page 2: ... all other warranties expressed or implied including warranties of merchantability or fitness for a particular purpose CAMPBELL SCIENTIFIC INC is not liable for special indirect incidental or consequential damages Products may not be returned without prior authorization The following contact information is for US and International customers residing in countries served by Campbell Scientific Inc d...

Page 3: ...tion 2 3 1 Site Selection 2 3 2 Mounting 2 4 Wiring 2 5 Programming 2 5 1 Programming Overview 2 5 2 Measurement Programming 3 5 3 Correction of Ionization Errors in EC Measurement 4 5 4 Correction of Temperature Errors 5 5 5 Output Processing 5 6 Calibration 5 6 1 Conversion Factors 5 6 2 Typical Ranges 5 6 3 Factory Calibration 5 6 4 Field Calibration 6 7 Maintenance 7 8 Analysis of Errors 7 8 1...

Page 4: ...10 Instruction 11 Details 9 11 Electrically Noisy Environments 10 12 Long Lead Lengths Temperature 10 ...

Page 5: ...Engineering physical chemistry texts and other sources 1 1 EC SENSOR The EC sensor consists of three stainless steel rings mounted in an epoxy tube as shown in Figure 4 1 Resistance of water passing through the tube is measured by excitation of the center electrode with positive and negative voltage The two outer electrodes return the signal to the datalogger This electrode configuration eliminate...

Page 6: ...ded by the stainless steel sleeve on the 247W L Strain on cables can be minimized by using a split mesh strain relief sleeve on the cable which is recommended for cables over 100 ft The strain relief sleeve is available from Campbell Scientific as part number 7421 4 WIRING The 247s manufactured after January 1 1994 are connected to a Campbell Scientific datalogger as illustrated in Figure 4 1 NOTE...

Page 7: ...1 Offset 02 P59 BR Transform Rf X 1 X 01 1 Rep 02 1 Loc Rs 03 1 Multiplier Rf Test the preliminary measurement against each case and make a refined measurement 03 P93 Case 01 1 Case Loc Rs 04 P 83 If Case Location F 01 1 8 F 02 30 Then Do 05 P5 AC Half Bridge 01 1 Rep 02 15 2500 mV fast Range Use 5000 mV fast for 21X 03 2 IN Chan 04 1 Excite all reps w EXchan 1 05 2500 mV Excitation Use 5000 mV fo...

Page 8: ...s entered in place of nnn in this segment 20 P42 Z 1 X 01 1 X Loc Rs 02 2 Z Loc 1 Rs 21 P37 Z X F 01 2 X Loc 1 Rs 02 nnn F ENTER CELL CONSTANT 03 3 Z Loc Ct Temperature Temperature is measured with a single instruction P11 that measures the thermistor resistance and calculates temperature Output is C when a multiplier of 1 and an offset of 0 is used See Section 10 for detailed information on the f...

Page 9: ... 100 F 03 9 Z Loc TC PROCES 33 P38 Z X F 01 8 X Loc 100 Ct 02 9 Y Loc TC PROCES 03 10 Z Loc C25mScm 1 5 5 OUTPUT PROCESSING Over large ranges EC is not linear and is best reported as samples 70 In limited ranges averaging 71 measurements over time may be acceptable Convention requires that the temperature at the time of the measurement be reported 6 CALIBRATION 6 1 CONVERSION FACTORS 1 S Siemens 1...

Page 10: ... 58 corrects for temperature errors within this range The solution constant of 1 408 mS cm 1 entered in step 13 37 is valid only for a 0 01 molal KCl solution Location 8 generated by step 14 will contain the resultant cell constant 01 P5 AC Half Bridge 01 1 Rep 02 15 2500 mV fast Range 5000 mV fast for 21X 03 2 IN Chan 04 1 Excite all reps w EXchan 1 05 2500 mV Excitation 5000 mV for 21X 06 1 Loc ...

Page 11: ...Solutions After Correction 2 0 0 45 to 7 0 mS cm 1 8 0 0 005 to 0 45 mS cm 1 Correction of Ionization Errors Figures 8 1 1 and 8 1 2 show the amount of correction applied by the example program to compensate for ionization effects on the measurements Also shown is an ideal correction Factors were derived by measuring the standard solutions described in Section 2 2 with values of 0 0234 0 07 0 4471...

Page 12: ...Table 8 2 1 For the range of 0 to 50 C the interchangeability error is predominantly offset and can be determined with a single point calibration Compensation can then be done with an offset entered in the measurement instruction The bridge resistors are 0 1 tolerance with a 10 ppm temperature coefficient Polynomial errors are tabulated in Table 8 2 2 and plotted in Figure 8 2 1 TABLE 8 2 1 Thermi...

Page 13: ... calculates the ratio of voltage measured to excitation voltage Vs Vx which is related to resistance as shown below Vs Vx 1000 Rs 249000 1000 where Rs is the resistance of the thermistor See the measurement section of the datalogger manual for more information on bridge measurements Instruction 11 then calculates temperature using a fifth order polynomial equation correlating Vs Vx with temperatur...

Page 14: ...r entries will vary with program and datalogger channel and input location assignments On the 21X and CR7 use the 15 mV input range and 4000 mV excitation 12 LONG LEAD LENGTHS TEMPERATURE If the 247 L 247W L has lead lengths of more than 300 feet use the DC Half Bridge instruction Instruction 4 with a 2 millisecond delay to measure temperature The delay provides a longer settling time before the m...

Page 15: ...247 CONDUCTIVITY AND TEMPERATURE PROBES 11 13 247 SCHEMATIC FIGURE 11 1 247 Conductivity and Temperature Circuit Diagram ...

Page 16: ...247 CONDUCTIVITY AND TEMPERATURE PROBES 12 This is a blank page ...

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Page 18: ... campbellsci com br suporte campbellsci com br Campbell Scientific Canada Corp CSC 11564 149th Street NW Edmonton Alberta T5M 1W7 CANADA www campbellsci ca dataloggers campbellsci ca Campbell Scientific Ltd CSL Campbell Park 80 Hathern Road Shepshed Loughborough LE12 9GX UNITED KINGDOM www campbellsci co uk sales campbellsci co uk Campbell Scientific Ltd France Miniparc du Verger Bat H 1 rue de Te...

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