Campbell 4WPB100 User manual

Revision:05/2020
Copyright © 1996 – 2020
Campbell Scientific
CSL I.D - 340

Guarantee
This equipment is guaranteed against defects in materials and workmanship.
We will repair or replace products which prove to be defective during the
guarantee period as detailed on your invoice, provided they are returned to us
prepaid. The guarantee will not apply to:

Equipment which has been modified or altered in any way without the
written permission of Campbell Scientific

Batteries

Any product which has been subjected to misuse, neglect, acts of God or
damage in transit.
Campbell Scientific will return guaranteed equipment by surface carrier
prepaid. Campbell Scientific will not reimburse the claimant for costs incurred
in removing and/or reinstalling equipment. This guarantee and the Company’s
obligation thereunder is in lieu of all other guarantees, expressed or implied,
including those of suitability and fitness for a particular purpose. Campbell
Scientific is not liable for consequential damage.
Please inform us before returning equipment and obtain a Repair Reference
Number whether the repair is under guarantee or not. Please state the faults as
clearly as possible, and if the product is out of the guarantee period it should
be accompanied by a purchase order. Quotations for repairs can be given on
request. It is the policy of Campbell Scientific to protect the health of its
employees and provide a safe working environment, in support of this policy a
“Declaration of Hazardous Material and Decontamination” form will be
issued for completion.
When returning equipment, the Repair Reference Number must be clearly
marked on the outside of the package. Complete the “Declaration of
Hazardous Material and Decontamination” form and ensure a completed copy
is returned with your goods. Please note your Repair may not be processed if
you do not include a copy of this form and Campbell Scientific Ltd reserves
the right to return goods at the customers’ expense.
Note that goods sent air freight are subject to Customs clearance fees which
Campbell Scientific will charge to customers. In many cases, these charges are
greater than the cost of the repair.
Campbell Scientific Ltd,
80 Hathern Road,
Shepshed, Loughborough, LE12 9GX, UK
Tel: [phone]
Fax: [phone]
Email: [e-mail]
www.campbellsci.co.uk

PLEASE READ FIRST
About this manual
Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the North
American market. Some spellings, weights and measures may reflect this origin.
Some useful conversion factors:
Area: 1 in2(square inch) = 645 mm2
Length: 1 in. (inch) = 25.4 mm
1 ft (foot) = 304.8 mm
1 yard = 0.914 m
1 mile = 1.609 km
Mass: 1 oz. (ounce) = 28.35 g
1 lb (pound weight) = 0.454 kg
Pressure: 1 psi (lb/in2) = 68.95 mb
Volume: 1 UK pint = 568.3 ml
1 UK gallon = 4.546 litres
1 US gallon = 3.785 litres
In addition, while most of the information in the manual is correct for all countries, certain information
is specific to the North American market and so may not be applicable to European users.
Differences include the U.S standard external power supply details where some information (for
example the AC transformer input voltage) will not be applicable for British/European use. Please note,
however, that when a power supply adapter is ordered it will be suitable for use in your country.
Reference to some radio transmitters, digital cell phones and aerials may also not be applicable
according to your locality.
Some brackets, shields and enclosure options, including wiring, are not sold as standard items in the
European market; in some cases alternatives are offered. Details of the alternatives will be covered in
separate manuals.
Part numbers prefixed with a “#” symbol are special order parts for use with non-EU variants or for
special installations. Please quote the full part number with the # when ordering.
Recycling information
At the end of this product’s life it should not be put in commercial or domestic refuse but
sent for recycling. Any batteries contained within the product or used during the
products life should be removed from the product and also be sent to an appropriate
recycling facility.
Campbell Scientific Ltd can advise on the recycling of the equipment and in some cases
arrange collection and the correct disposal of it, although charges may apply for some
items or territories.
For further advice or support, please contact Campbell Scientific Ltd, or your local agent.
Campbell Scientific Ltd, 80 Hathern Road, Shepshed, Loughborough, LE12 9GX,
UK Tel: [phone] Fax: [phone]
Email: [e-mail]
www.campbellsci.co.uk

Safety
DANGER —MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON
OR AROUND TRIPODS, TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS,
CROSSARMS, ENCLOSURES, ANTENNAS, ETC. FAILURE TO PROPERLY AND COMPLETELY ASSEMBLE,
INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS, TOWERS, AND ATTACHMENTS, AND FAILURE TO HEED
WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS INJURY, PROPERTY DAMAGE, AND
PRODUCT FAILURE. TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS. CHECK WITH YOUR
ORGANIZATION'S SAFETY COORDINATOR (OR POLICY) FOR PROCEDURES AND REQUIRED PROTECTIVE
EQUIPMENT PRIOR TO PERFORMING ANY WORK.
Use tripods, towers, and attachments to tripods and towers only for purposes for which they are designed. Do not
exceed design limits. Be familiar and comply with all instructions provided in product manuals. Manuals are
available at www.campbellsci.eu or by telephoning [phone] (UK). You are responsible for conformance
with governing codes and regulations, including safety regulations, and the integrity and location of structures or land
to which towers, tripods, and any attachments are attached. Installation sites should be evaluated and approved by a
qualified engineer. If questions or concerns arise regarding installation, use, or maintenance of tripods, towers,
attachments, or electrical connections, consult with a licensed and qualified engineer or electrician.
General
•Prior to performing site or installation work, obtain required approvals and permits. Comply with all
governing structure-height regulations, such as those of the FAA in the USA.
•Use only qualified personnel for installation, use, and maintenance of tripods and towers, and any
attachments to tripods and towers. The use of licensed and qualified contractors is highly recommended.
•Read all applicable instructions carefully and understand procedures thoroughly before beginning work.
•Wear a hardhat and eye protection, and take other appropriate safety precautions while working on or
around tripods and towers.
•Do not climb tripods or towers at any time, and prohibit climbing by other persons. Take reasonable
precautions to secure tripod and tower sites from trespassers.
•Use only manufacturer recommended parts, materials, and tools.
Utility and Electrical
•You can be killed or sustain serious bodily injury if the tripod, tower, or attachments you are installing,
constructing, using, or maintaining, or a tool, stake, or anchor, come in contact with overhead or
underground utility lines.
•Maintain a distance of at least one-and-one-half times structure height, or 20 feet, or the distance
required by applicable law, whichever is greater, between overhead utility lines and the structure (tripod,
tower, attachments, or tools).
•Prior to performing site or installation work, inform all utility companies and have all underground utilities
marked.
•Comply with all electrical codes. Electrical equipment and related grounding devices should be installed
by a licensed and qualified electrician.
Elevated Work and Weather
•Exercise extreme caution when performing elevated work.
•Use appropriate equipment and safety practices.
•During installation and maintenance, keep tower and tripod sites clear of un-trained or non-essential
personnel. Take precautions to prevent elevated tools and objects from dropping.
•Do not perform any work in inclement weather, including wind, rain, snow, lightning, etc.
Maintenance
•Periodically (at least yearly) check for wear and damage, including corrosion, stress cracks, frayed cables,
loose cable clamps, cable tightness, etc. and take necessary corrective actions.
•Periodically (at least yearly) check electrical ground connections.
WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL
SCIENTIFIC PRODUCTS, THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER
INSTALLATION, USE, OR MAINTENANCE OF TRIPODS, TOWERS, OR ATTACHMENTS TO TRIPODS AND TOWERS
SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC.

Table of contents
1. Function 1
2. Specifications 2
3. Wiring 3
4. Programming examples 4
4.1 GRANITE 9/10 program example 5
4.2 GRANITE 6/CR6 program example 6
4.3 CR1000X program example 6
4.4 CR1000 program example 7
4.5 CR9000X program example 7
5. PRT in 4-wire half bridge 8
5.1 Excitation voltage 9
5.2 Calibrating a PRT 9
Table of Contents - i

1. Function
A terminal input module (TIM) connects directly to a data logger or GRANITE analogue input
module. It provides completion resistors for resistive bridge measurements, voltage dividers, and
precision current shunts. The 4WPB100 and 4WPB1K are used to provide completion resistors for
4 wire half bridge measurements of 100 Ω and 1 kΩ platinum resistance thermometer (PRT),
respectively.
NOTE:
The GRANITE 6 and CR6 include the fixed resistor and current excitation required to complete
the half-bridge circuit without a terminal input module. However, the GRANITE 6 and CR6
are still compatible with a terminal input module and may be used with one, should the
application require it.
FIGURE 1-1. Terminal input module
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 1

2. Specifications
Current limiting 10 kΩ resistor
Tolerance @ 25 °C: ±5%
Power rating: 0.25 W
Completion resistor
Tolerance @ 25 °C: ±0.01%
Maximum temperature
coefficient
±0.8 ppm/°C
Power rating @ 70 °C: 0.25 W
EU certificate of conformity: https://s.campbellsci.ceu/documents/eu/compliance/eudoc_
terminal-input-modules.pdf
FIGURE 2-1. Circuit schematic
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 2

3. Wiring
When making 4-wire half bridge measurements, the 4WPB is connected to adjacent Hand L
terminals to perform a differential measurement. The sense wires from the PRT (indicated by
dashed lines in FIGURE 3-1 (p. 3) are connected to a second pair of Hand Lterminals to perform
a differential measurement. The black excitation wire is connected to an excitation terminal. In
the following example, the 4WPB is connected to the 1H and 1L terminals, and the PRT to the 2H
and 2L terminals. The excitation wire is connected to the VX1 terminal.
FIGURE 3-1. Wiring for example program
The terminal spacing of the GRANITE 6 and GRANITE analogue input module is different than
other data loggers. The terminal input modules are still compatible, but the pins must be gently
bent inward a small amount to allow the terminal input module to be mounted.
It is still possible to use terminal input modules in adjacent terminal blocks if the modules are
staggered. This is done by gently bending one module forward and the next terminal backward
enough to clear the first module. Continue to alternate the modules as needed.
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 3

Table 3-1: 4WPB100/4WPB1K connections to Campbell Scientific data loggers
Function Label/Wire
GRANITE
analogue
input module
GRANITE6,
CR6
CR3000,
CR1000X,
CR800, CR850,
CR1000
CR9000X
Excitation Black wire X1 U5 VX1 Excitation 1
V1 high H 1H U1 1H 1H
V1 low L 1L U2 1L 1L
Ground G ⏚ ⏚ ⏚ ⏚
1 The GRANITE 9 and GRANITE 10 do not directly make analogue measurements. Instead, they use analogue input
modules such as the VOLT 108 or VOLT 116. When making a half-bridge measurement, the terminal input module is
connected to the analogue input module, which is then connected to the GRANITE 9 or GRANITE 10.
4. Programming examples
The following examples show the two instructions necessary to 1) make the measurement and 2)
calculate the temperature. The result of the half bridge measurement as shown is Rs/R0, the input
required for the PRT algorithm to calculate temperature.
If using a calibrated sensor, the exact measurement of R0will be known. Use this value to
increase the accuracy of the PRTCalc() instruction by inserting the following equation
between the BrHalf4W() and PRTCalc() instructions in the example programs.
Rs_R0 = Rs_R0*100/R0
where R0 is the sensor resistance at 0 °C
The following examples are for a 100 Ω PRT and 4WPB100. The excitation voltages used were
chosen with the assumption that the temperature would not exceed 50 °C. Calculation of
optimum excitation voltage is discussed in Excitation voltage (p. 9). Using the 4WPB1K allows for
a higher excitation voltage.
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 4

4.1 GRANITE 9/10 program example
The GRANITE9 and GRANITE10 require the use of an analogue input module, such as
the VOLT108, when making a half-bridge measurement.
CRBasic Example 1: GRANITE9/10 4-wire half bridge example
'4-wire half bridge example
'GRANITE 9 and GRANITE 10 data loggers (with a VOLT 108)
'Declare Variables and Units
Public Temp_C_4wire
Public Rs_R0
'Define Data Tables
DataTable(Hourly,True,-1)
DataInterval(0,60,Min,10)
Average(1,Temp_C_4wire,IEEE4,False)
EndTable
'Main Program
BeginProg
'Configure the VOLT 108 Module and assign it CPI address 'CPI_BUSA+1'
CPIAddModule(VOLT108,10," ",CPI_BUSA+1)
'Main Scan
Scan(5,Sec,1,0)
'Half Bridge, 4-wire measurements on the VOLT 108
CDM_BrHalf4W(VOLT108,CPI_BUSA+1,Rs_R0,1,mV1000,mV1000,1,1,1,400, _
True,True,500,60,1,0)
'PRT temperature calculation
PRTCalc (Temp_C_4wire,1,Rs_R0,0,1.0,0)
'Call Data Tables and Store Data
CallTable Hourly
NextScan
EndProg
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 5

4.2 GRANITE 6/CR6 program example
The GRANITE 6 and CR6 include the fixed resistor and current excitation required to complete
the half-bridge circuit without a terminal input module. However, the GRANITE 6 and CR6 are
still compatible with a terminal input module and may be used with one, should the application
require it.
CRBasic Example 2: GRANITE 6/CR6 4-wire half bridge example
'GRANITE 6/CR6 data logger 4-wire half bridge
Public Rs_R0, Temp_C
DataTable (Hourly,True,-1)
DataInterval (0,60,Min,0)
Average (1,Temp_C,IEEE4,0)
EndTable
BeginProg
Scan (1,Sec,0,0)
BrHalf4W (Rs_R0,1,mV1000,mV1000,U1,U5,1,400,True ,True ,0,250,1.0,0)
PRTCalc (Temp_C,1,Rs_R0,0,1,0)
CallTable Hourly
NextScan
EndProg
4.3 CR1000X program example
CRBasic Example 3: CR1000X 4-wire half bridge example
'CR1000X-series data logger 4-wire half bridge
Public Rs_R0, Temp_C
DataTable (Hourly,True,-1)
DataInterval (0,60,Min,0)
Average (1,Temp_C,IEEE4,0)
EndTable
BeginProg
Scan (1,Sec,0,0)
BrHalf4W (Rs_R0,1,mV1000,mV1000,1,Vx1,1,400,True ,True ,0,250,1.0,0)
PRTCalc (Temp_C,1,Rs_R0,0,1,0)
CallTable Hourly
NextScan
EndProg
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 6

4.4 CR1000 program example
CRBasic Example 4: CR1000 4-wire half bridge example
'CR1000-series data logger 4-wire half bridge
Public Rs_R0, Temp_C
DataTable (Hourly,True,-1)
DataInterval (0,60,Min,0)
Average (1,Temp_C,IEEE4,0)
EndTable
BeginProg
Scan (1,Sec,0,0)
BrHalf4W(Rs_R0,1,mV250,mV250,1,Vx1,1,2500,True,True,0,250,1.0,0)
PRTCalc (Temp_C,1,Rs_R0,0,1,0)
CallTable Hourly
NextScan
EndProg
4.5 CR9000X program example
CRBasic Example 5: CR9000X 4-wire half bridge example
'CR9000X data logger 4-wire half bridge
Public Rs_Ro, Temp_F
DataTable (Temp_F,1,-1)
DataInterval (0,0,0,10)
Sample (1,Temp_F,FP2)
EndTable
BeginProg
Scan (1,mSec,0,0)
BrHalf4W (Rs_Ro,1,mV1000,mV1000,4,1,5,7,1,400,True,True,30,40,1.0,0)
PRTCalc (Temp_F,1,Rs_Ro,0,1.8,32)
CallTable Temp_F
NextScan
EndProg
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 7

5. PRT in 4-wire half bridge
A 4-wire half bridge is the best choice for accuracy where the platinum resistance thermometer
(PRT) is separated from other bridge completion resistors by a wire length having more than a
few thousandths of an Ohm resistance. Four wires to the sensor allows one set of wires to carry
the excitation current with a separate set of sense wires allowing the voltage across the PRT to be
measured without the effect of any voltage drop in the excitation wires. This arrangement cancels
out both the effect of the wire length and differences in resistance of the excitation wires going
out to and returning from the sensor.
FIGURE 2-1 (p. 2) shows the circuit used to measure the PRT. The 10 kΩ resistor allows the use of
a high excitation voltage and low voltage ranges on the measurements. This ensures noise in
the excitation does not have an effect on signal noise, and that self heating of the PRT due to
excitation is kept to a minimum. Because the fixed resistor (Rf) and the PRT (Rs) have
approximately the same resistance, the differential measurement of the voltage drop across the
PRT can be made on the same range as the differential measurement of the voltage drop across
Rf.
The result of the four wire half bridge Instruction is:
the voltage drop is equal to the current (I), times the resistance thus:
The PRTCalc() instruction computes the temperature (°C) for a DIN 43760 standard PRT from
the ratio of the PRT resistance at the temperature being measured (Rs) to its resistance at 0°C
(R0). Thus, a multiplier of Rf/R0is used with the 4-wire half bridge instruction to obtain the
desired intermediate, Rs/R0= (Rs/Rfx Rf/R0). If Rfand R0are equal, the multiplier is 1.
The fixed resistor must be thermally stable. The 0.8ppm/°C temperature coefficient would result
in a maximum error of 0.035°C at 125°C. This measurement is ratiometric (Rs/Rf) and does not
rely on the absolute values of either Rsor Rf.
The properties of the 10 kΩ resistor do not affect the result. The purpose of this resistor in the
circuit is to limit current.
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 8

5.1 Excitation voltage
When determining the excitation voltage, it is important to consider the maximum excitation
current the sensor can experience without self-heating. This is typically less than 0.35 mA. Refer
to the manufacturer's data sheet for the sensor for the specific value.
Once the maximum excitation current is known, the excitation voltage is then calculated.
Vx= Ix(R1+ RSmax + Rf)
Where:
R1= 10 kΩ, the current limiting resistor in the terminal input module
RSmax = Maximum sensor resistance based on the maximum expected temperature to be
measured
Rf= PRT completion resistor value
Using the typical 0.35 mA maximum excitation current, the maximum excitation voltage for the
sensor is:
4WPB100
Vx= 0.35 mA (10,000 Ω + 125 Ω + 100 Ω) = 3579 mV
4WPB1K
Vx= 0.35 mA (10,000 Ω + 1250 Ω + 1000 Ω) = 4290 mV
Small variations in sensor resistance do not cause significant differences in the calculated
maximum excitation voltage. For example, changing the sensor resistance to 84Ω when used
with the 4WPB100 reduces the maximum excitation from 3579mV to 3564mV.
5.2 Calibrating a PRT
The greatest source of error in a PRT is likely to be that the resistance at 0°C deviates from the
nominal value. Calibrating the PRT in an ice bath can correct this offset and any offset in the
fixed resistor in the terminal input module.
The result of the 4 wire half bridge is:
With the PRT at 0°C, Rs=R0. Thus, the above result becomes R0/Rf, the reciprocal of the
multiplier required to calculate temperature, Rf/R0. By making a measurement with the PRT in an
ice bath, errors in both Rsand R0can be accounted for.
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 9

To perform the calibration, connect the PRT to the data logger and program the data logger to
measure the PRT with the 4-wire half bridge as shown in the example section (multiplier = 1).
Place the PRT in an ice bath (@ 0°C; Rs=R0). Read the result of the bridge measurement. The
reading is Rs/Rf, which is equal to R0/Rfsince Rs=R0. The correct value of the multiplier, Rf/R0, is
the reciprocal of this reading. For example, if the initial reading is 0.9890, the correct multiplier is:
Rf/R0= 1/0.9890 = 1.0111.
4WPB100, 4WPB1K PRT Bridge Terminal Input Modules 10