CS526 ISFET pH Probe
2/12
C o p y r i g h t © 2 0 0 9 - 2 0 1 2
C a m p b e l l S c i e n t i f i c , I n c .
Warranty
The CS526 ISFET pH Probe is warranted for six (6) months subject to this
limited warranty:
“PRODUCTS MANUFACTURED BY CAMPBELL SCIENTIFIC, INC. are
warranted by Campbell Scientific, Inc. (“Campbell”) to be free from defects in
materials and workmanship under normal use and service for twelve (12)
months from date of shipment unless otherwise specified in the corresponding
Campbell pricelist or product manual. Products not manufactured, but that are
re-sold by Campbell, are warranted only to the limits extended by the original
manufacturer. Batteries, fine-wire thermocouples, desiccant, and other
consumables have no warranty. Campbell's obligation under this warranty is
limited to repairing or replacing (at Campbell's option) defective products,
which shall be the sole and exclusive remedy under this warranty. The
customer shall assume all costs of removing, reinstalling, and shipping
defective products to Campbell. Campbell will return such products by surface
carrier prepaid within the continental United States of America. To all other
locations, Campbell will return such products best way CIP (Port of Entry)
INCOTERM® 2010, prepaid. This warranty shall not apply to any products
which have been subjected to modification, misuse, neglect, improper service,
accidents of nature, or shipping damage. This warranty is in lieu of all other
warranties, expressed or implied. The warranty for installation services
performed by Campbell such as programming to customer specifications,
electrical connections to products manufactured by Campbell, and product
specific training, is part of Campbell’s product warranty. CAMPBELL
EXPRESSLY DISCLAIMS AND EXCLUDES ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. Campbell is not liable for any special, indirect,
incidental, and/or consequential damages.”
Assistance
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. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company serves
your country.
To obtain a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone (435) 227-2342. After an applications engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container. Campbell
Scientific's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
For all returns, the customer must fill out a "Statement of Product Cleanliness
and Decontamination" form and comply with the requirements specified in it.
The form is available from our web site at www.campbellsci.com/repair. A
completed form must be either emailed to repair@campbellsci.com or faxed to
(435) 227-9579. Campbell Scientific is unable to process any returns until we
receive this form. If the form is not received within three days of product
receipt or is incomplete, the product will be returned to the customer at the
customer's expense. Campbell Scientific reserves the right to refuse service on
products that were exposed to contaminants that may cause health or safety
concerns for our employees.
CS526 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. Introduction..................................................................1
2. Cautionary Statements................................................1
3. Initial Inspection ..........................................................1
4. Quickstart .....................................................................2
5. Overview.......................................................................3
6. Specifications ..............................................................3
7. Installation and Wiring ................................................4
7.1 Preparation for Use...................................................................................4
7.2 Wiring.......................................................................................................4
8. Programming ...............................................................4
8.1 Get Data Command ..................................................................................4
8.2 CRBasic Programming .............................................................................5
8.2.1 Instruction Sequence.......................................................................5
8.2.2 Instruction Descriptions ..................................................................6
8.2.2.1 SerialOpen() Instruction........................................................6
8.2.2.2 SerialOut Instruction .............................................................6
8.2.2.3 SerialIn Instruction................................................................6
8.2.2.4 SplitStr Instruction ................................................................7
8.2.3 Example Program............................................................................7
8.2.4 Programming for Calibration ..........................................................7
9. Calibration ....................................................................7
10. Troubleshooting ........................................................8
11. Maintenance ...............................................................9
i
CS526 Table of Contents
Appendix
A. Calibration................................................................ A-1
Figure
11-1. Tip of the CS526 Probe ...................................................................... 10
Tables
7-1.
8-1.
8-2.
9-1.
CR800, CR850, CR1000, and CR3000 Wiring...................................... 4
Get Data Command and Response ......................................................... 5
Instruction Sequence............................................................................... 5
Calibration Standards ............................................................................. 8
ii
CS526 ISFET pH Probe
1. Introduction
The CS526 ISFET pH Probe measures pH from 0 to 14 in aqueous or semisolid solutions. It outputs TTL serial data that is read by compatible
dataloggers (see Section 6 Specifications).
Before using the CS526, please study
• Section 2. Cautionary Statements
• Section 3. Initial Inspection
• Section 4. Quickstart
More detailed instructions for operation, troubleshooting, and maintenance are
available in the remaining sections.
2. Cautionary Statements
•
Maximum input voltage is 5 Vdc. Incorrect wiring may cause loss of
performance and irreversible damage.
•
To prevent scratching the sensor chip when cleaning, first soak the sensor in
soapy water, then gently scrub with a toothbrush (see Section 11.
Maintenance). Most scratches occur when hard particles are rubbed on the
chip surface. Scratches cause irreversible damage to the probe.
•
The CS526 is rugged, but it should be handled as a precision scientific
instrument.
•
The CS526 has no user-serviceable parts. Any attempt to disassemble the
device will void the six-month warranty.
•
Care should be taken when opening the shipping package to not damage or cut
the cable jacket. If damage to the cable is suspected, consult with a Campbell
Scientific applications engineer.
3. Initial Inspection
Upon receipt of the CS526, inspect the packaging and contents for damage.
File damage claims with the shipping company.
The model number and cable length are printed on a label at the connection
end of the cable. Check this information against the shipping documents to
ensure the correct product and cable length are received.
1
CS526 ISFET pH Probe
4. Quickstart
For complete installation, programming, and calibration information, see
Sections 7 through 9.
The CS526 is shipped dry. Before the probe can be calibrated, it must be
soaked in 7 pH buffer solution for 15 minutes. Follow the calibration
procedure outlined in Appendix A.
Unlike many glass-bulb type pH sensors, the CS526 ISFET pH probe can be
installed without regard to orientation. Connect the CS526 to the datalogger
according to the following table. Be sure to connect Red to the 5V channel.
Wire Color
Datalogger Connection
Red (Caution! 5 Vdc Max!)
5V
Black
G
White
Control Port (Tx)
Green
Control Port (Rx)
Clear
G
Program the datalogger as follows.
'CR1000 Series Datalogger
'Declare variable for PH measurement in mV
Public pHmV
'Declare variables for serial input from sensor
Dim rawstring As String * 20, pHDigit(2)
'Main Program
BeginProg
'Set up one of the datalogger's ports for serial communication
SerialOpen ( Com1,2400,16,0,41)
'Establish program scan rate of 60 seconds
Scan (60,Sec,0,0)
'Send get data command to CS526
SerialOut (Com1,"1M1!"&CHR(13),"",0,0)
'Set up COM1 to receive incoming serial data.
'Set timeout to maximum 200mS
SerialIn (rawstring,Com1,20,0,20)
'Split out numeric mV value for PH from string input
SplitStr (pHDigit(),rawstring,"String",2,0)
pHmV = pHDigit(2)
NextScan
EndProg
2
CS526 ISFET pH Probe
5. Overview
The submersible CS526 is designed to reliably provide accurate temperature
compensated pH measurements. The pH-sensitive element is SENTRON's Ion
Sensitive Field Effect Transistor (ISFET) semi-conductor, which includes a
silver / silver chloride - potassium chloride reference system. This technology
is the most significant breakthrough in pH testing in half a century and is the
most powerful pH testing technology available today.
The CS526 is suitable for demanding applications in laboratory and field. The
ISFET performs well in solutions with high solids, moderately aggressive
chemicals, and biological materials. Clogging and junction contaminating
conditions are well tolerated. See Section 11 Maintenance for cleaning
procedures.
CS526 electronics are embedded in durable PEEK material, which makes up
the sensor body. The absence of a glass electrode eliminates the potential
hazard of broken glass. The ISFET design considerably reduces the number of
acidic or alkaline errors in extreme pH conditions.
6. Specifications
Features
•
Safety — the ISFET with durable PEEK material can be used safely in
applications where broken glass is a hazard to the user.
•
Intelligent electronics — the CS526 combines the latest developments in
ISFET pH sensing technology with state-of-the-art signal processing.
This allows for accurate, fast and reliable results.
•
Quality — designed and manufactured under stringent quality control
conditions in an ISO 9001 environment. Each sensor is individually tested
to the most demanding testing protocols, and the electronics comply fully
directives and with EMC standard IEC61326:2005.
with
Compatibility:
CR800 / 850, CR1000, CR3000 dataloggers
Measurement
Range:
Accuracy:
24 hr drift:
1 to 14 pH
±0.2 pH with 2 point calibration
< 0.15 pH (after 15 min soak in pH 7 at 25°C)
Operating
Temperature:
Water Pressure:
10° to 40°C
0 to 700 kPa (0 to 101.5 psi)
Storage Temperature:
20° to 30°C
Power Requirement
Source:
Load:
5 Vdc
15 mA maximum
Output:
TTL logic, 2400 bps
8 data bits, no parity, 1 stop bit
3
CS526 ISFET pH Probe
Maximum Cable Length:
100 m (328 ft)
Cable Type:
Three-twisted pair, 24 awg cable with
Santoprene® jacket
Sensor Material:
PEEK
Weight
w/10 ft Cable:
Dimensions
Length:
Diameter:
318 g (11.2 oz)
102 mm (4 in)
16 mm (0.63 in)
Certifications:
ISO 9001
compliant
EMC standard IEC61326:2005
7. Installation and Wiring
7.1 Preparation for Use
The CS526 is shipped dry. Before the probe can be calibrated, soak it in 7 pH
buffer solution for 15 minutes. Unlike many glass-bulb type pH sensors, the
CS526 ISFET pH probe can be installed without regard to orientation.
7.2 Wiring
TABLE 7-1. CR800, CR850, CR1000, and CR3000 Wiring
CAUTION
Wire Color
Wire Label/Function
Datalogger Connections
Red (see following
caution)
Power 5V
5V
Black
Ground
G
White
Signal #1 (Tx)
Control Port (Tx)
Green
Signal #2 (Rx)
Control Port (Rx)
Clear
Shield
G
This probe must be connected to the datalogger’s 5V
terminal (not 12V). Connecting to a higher voltage will
damage the probe beyond repair.
8. Programming
8.1 Get Data Command
The datalogger needs to send a “get data” serial command to the CS526 to get
the pH data. This command is sent to the CS526 via the SerialOut() CRBasic
4
CS526 ISFET pH Probe
instruction (see Section 8.2.2.2). Table 8-1 shows the “get data” command and
its response.
TABLE 8-1. Get Data Command and Response
Command
Response
aMn!<CR>
a<value><CR><LF>
Where:
a = probe address (factory
default is 1)
n = a single dummy character
(typically use 1)
Where:
a = probe address (factory default is 1)
<value> = the probe’s reading for pH (in
millivolts).
8.2 CRBasic Programming
8.2.1 Instruction Sequence
A sequence of CRBasic instructions are used to measure the sensor. Table
8-2 shows the instruction sequence. Information about the instructions is
provided in Section 8.2.2 and an example program is provided in Section 8.2.3.
TABLE 8-2. Instruction Sequence
Instruction
Function
SerialOpen()
Set up a datalogger port for serial communication (see
Section 8.2.2.1)
Scan()
Establish a scan rate
SerialOut()
Send “get data” command to the CS526.
See Section 8.1 and 8.2.2.2 for more information.
SerialIn()
Set up the COM port to receive the incoming serial data (see
Section 8.2.2.3).
Please note that in the beginning of the CRBasic program, the
variable used in the SerialIn instruction needs to be declared
as an ASCII string format.
SplitStr()
NOTE
Split out numeric millivolt value for pH from the input string.
Probe output is “Counts”. A corrected multiplier and offset are
required to provide an output in pH units (see Appendix A).
5
CS526 ISFET pH Probe
8.2.2 Instruction Descriptions
8.2.2.1 SerialOpen() Instruction
The SerialOpen() instruction has the following syntax:
SerialOpen(ComPort,BaudRate,Format,TXDelay,BufferSize)
ComPort — the datalogger COM port to which the probe is connected.
BaudRate — choose 2400
Format — choose 16, which is TTL Logic; No parity, one stop bit, 8 data
bits; No error checking
TXDelay — enter 0
BufferSize — enter at least twice the number of maximum expected
characters + 1, which is 41.
8.2.2.2 SerialOut Instruction
The SerialOut() instruction has the following syntax:
SerialOut(ComPort,OutString,WaitString,NumberTries,TimeOut)
ComPort — the datalogger COM port in which the probe is connected.
OutString — use "1M1!"+CHR(13) for the OutString when the default
probe address of 1 is used.
WaitString — enter the null (“”) WaitString to tell the datalogger to wait
for the echo of each character in the OutString
NumberTries — enter 0
TimeOut — specifies the time, in 0.01 seconds, that the datalogger should
wait for the WaitString or echo of each character in the OutString (0
is used in the example program).
8.2.2.3 SerialIn Instruction
The SerialIn() instruction has the following syntax:
SerialIn(Dest,ComPort,TimeOut,TerminationChar,MaxNumChars)
Dest — specifies the variable in which the incoming data will be stored.
Please note that in the beginning of the CRBasic program, this
variable needs to be declared as ASCII string format (see example
program in Section 8.2.3)
ComPort — the datalogger COM port in which the probe is connected.
TimeOut — 20 should be adequate, which gives a 200 ms maximum delay
time. The TimeOut parameter is used to specify the amount of time,
in 0.01 seconds, that the datalogger should wait before proceeding to
the next instruction.
TerminationChar — enter 0
MaxNumChars — 20 should be adequate (specify the maximum number
of characters to expect per input)
6
CS526 ISFET pH Probe
8.2.2.4 SplitStr Instruction
The SplitStr() instruction has the following syntax:
SplitStr(SplitResult,SearchString,FilterString,NumSplit,SplitOption)
SplitResult — an array in which the split string will be stored.
SearchString — the string on which this instruction will operate. This will
be the variable entered for the Dest parameter for the SerialIn
instruction (see above).
FilterString — enter “String” (this value will be ignored because of the
SplitOption that will be used).
NumSplit — enter 2
SplitOption — enter 0. This splits out numeric values.
8.2.3 Example Program
The following is a CR1000 program that measures the CS526. This program
assumes the CS526 is connected to COM1 (C1 / TX and C2 / RX) on the
CR1000.
'CR1000 Series Datalogger
'Declare variable for PH measurement in mV
Public pHCount
'Declare variables for serial input from sensor
Dim rawstring As String * 20, pHDigit(2)
'Main Program
BeginProg
'Set up one of the datalogger's ports for serial communication
SerialOpen ( Com1,2400,16,0,41)
'Establish program scan rate of 60 seconds
Scan (60,Sec,0,0)
'Send get data command to CS526
SerialOut (Com1,"1M1!"&CHR(13),"",0,0)
'Set up CR1000 COM1 to receive incoming serial data.
'Set timeout to maximum 200 ms
SerialIn (rawstring,Com1,20,0,20)
'Split out numeric mV value for pH from string input
SplitStr (pHDigit(),rawstring,"String",2,0)
pHCount = pHDigit(2)
NextScan
EndProg
8.2.4 Programming for Calibration
To output in pH units instead of millivolts, enter the offset and multiplier into
the datalogger program. Simple program instructions can be used to make the
required periodic calibration easier. See Appendix A for an example program.
9. Calibration
Calibration should be carried out according to the detailed procedure outlined
in Appendix A. The calibration should utilize two or more pH standards, listed
in Table 9-1, which are available from Campbell Scientific.
7
CS526 ISFET pH Probe
TABLE 9-1. Calibration Standards
pH
CSI Part Number
4
25587
7
25586
10
25588
Frequency of calibration depends on the level of accuracy required and the
coating / fouling nature of the measured samples.
10. Troubleshooting
The most common causes for erroneous pH data include:
• poor sensor connections to the datalogger
• damaged cables
• scratched chip
Problem:
Output signal is at its maximum value.
Possible reason:
o Probe is not in fluid.
o Chip is polluted.
o Diaphragm is polluted.
o Chip is scratched.
Suggestion:
o Put probe in fluid.
o Clean probe using soapy water method.
o Probe cannot be fixed if chip is scratched.
Problem:
Probe response is very slow.
Possible reason:
o Diaphragm is chipped or polluted.
Suggestion:
o Clean probe with soapy water method.
Problem:
Probe signal is drifting.
Possible reason:
o Diaphragm can be dried out.
o Chip is scratched.
Suggestion:
o Soak probe for 10 minutes in saturated KC1 solution (CSI PN
16349).
o Probe cannot be fixed.
8
CS526 ISFET pH Probe
11. Maintenance
Campbell Scientific recommends that the CS526 be cleaned and calibrated
periodically to insure accurate readings.
The CS526 has no user-serviceable parts.
If the CS526 is not operating properly and requires return to Campbell
Scientific, first obtain an RMA (returned material authorization) and fill out
the Declaration of Hazardous Material and Decontamination form. This
information is available at http://www.campbellsci.com/repair.
Cable can be damaged by abrasion, rodents, sharp objects, twisting, crimping
or crushing and pulling. Take care during installation and use to avoid cable
damage.
Contamination on the diaphragm may block the built-in reference electrode, so
there will be no electrical contact between the electrode and the ISFET chip.
This condition will cause the probe to not function. To prevent this, regular
cleaning is recommended. Frequency of cleaning depends on the quality of the
water. The best cleaning method is the “soapy water” method:
CAUTION
1.
Place the tip of the probe in soapy water that is 50° to 60°C and soak for
about 5 minutes (see Figure 11-1).
2.
Rinse thoroughly with deionized water.
3.
If necessary, lightly scrub the tip of the probe with a toothbrush to remove
debris (see following caution).
4.
Place the probe in saturated KC1 solution (CSI pn 16349) at about 20°C.
Keep probe in solution for about 30 minutes.
To prevent scratching the chip, a toothbrush should only
be used after soaking in soapy water. Most scratches
occur when hard particles are rubbed with a toothbrush on
the chip surface. This can cause irreversible damage to
the probe.
5.
Rinse the probe.
6.
Calibrate the probe (see Appendix A).
9
CS526 ISFET pH Probe
Diaphragm
Chip
FIGURE 11-1. Tip of the CS526 Probe
10
Appendix A. Calibration
This calibration process uses 7 pH and 4 pH buffer solutions.
NOTEProtect the sensing chip from UV radiation during calibration. If
calibrating in sun or fluorescent light, shield the sensing chip from UV
by using dark containers for the buffer solutions.
Load the following example CRBasic program into the datalogger. Wire the
CS526 to the datalogger according to the following diagram.
Wire Color
Datalogger Connection
Red (Caution! 5 Vdc Max!)
5V
Black
G
White
Control Port (Tx)
Green
Control Port (Rx)
Clear
G
Use the Numeric Display found in the datalogger software PC200W, PC400,
LoggerNet, PConnect, or PConnectCE to monitor the measurement in real
time.
1.
Place the CS526 into a pH 7 buffer solution (CSI pn 25586).
2.
Monitor the [pHmV] reading in the Numeric Display and allow it to
stabilize.
3.
Change the value in [pH7record] to -1.
4.
Remove the CS526 from the pH7 buffer solution and rinse with de-ionized
water.
5.
Blot the CS526 dry with a soft cloth or paper towel.
6.
Place the CS526 in a pH 4 buffer solution (CSI pn 25587).
7.
Allow the [pHmV] reading to stabilize.
8.
Change the value in [pH4record] to -1.
9.
Change the value in [pHcal] to -1.
10. The CS526 is now ready to be placed in the solution to be measured.
A-1
Appendix A. Calibration
Following is a simple example program to facilitate the two point calibration.
'CR1000 Series Datalogger
'Define Variables
Public pH, pHCount
Public PTemp, batt_volt
Public pH4record, pH4Count
Public pH7record, pH7Count
Public pHcal, pHmult1
Public pHoffset1
Dim rawstring As String * 20, pHDigit(2)
'Define Data Tables
DataTable (TenMin,1,-1)
DataInterval (0,10,Min,10)
Average (1,pH,FP2,False)
EndTable
'Main Program
BeginProg
SerialOpen (Com1,2400,16,0,41)
Scan (10,Sec,0,0)
PanelTemp (PTemp,250)
Battery (batt_volt)
SerialOut (Com1,"1M1!"&CHR(13),"",0,0)
SerialIn (rawstring,Com1,20,0,20)
SplitStr (pHDigit(),rawstring,"String",2,0)
pHCount = pHDigit(2)
'Calibration
If PH4record = -1 Then
pH4Count = pHCount
pH4record = 0
EndIf
If pH7record = -1 Then
pH7Count = pHCount
pH7record = 0
EndIf
If pHcal = -1 Then
pHmult1 = 3/(pH7Count - pH4Count)
pHoffset1 = 7 - pHmult1 * pH7Count
pHcal = 0
EndIf
pH = pHmult1 * pHCount + pHoffset1
CallTable TenMin
NextScan
EndProg
A-2
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