Campbell Scientific ASPTC User Manual

Model ASPTC Aspirated Shield

with Fine Wire Thermocouple

Revision: 6/10

Copyright © 1993-2010

Campbell Scientific, Inc.

Warranty and Assistance

The MODEL ASPTC ASPIRATED SHIELD WITH FINE WIRE
THERMOCOUPLE is warranted by Campbell Scientific, Inc. to be free from

defects in materials and workmanship under normal use and service for twelve
(12) months from date of shipment unless specified otherwise. Batteries have
no warranty. Campbell Scientific, Inc.'s obligation under this warranty is
limited to repairing or replacing (at Campbell Scientific, Inc.'s option)
defective products. The customer shall assume all costs of removing,
reinstalling, and shipping defective products to Campbell Scientific, Inc.
Campbell Scientific, Inc. will return such products by surface carrier prepaid.
This warranty shall not apply to any Campbell Scientific, Inc. products which
have been subjected to modification, misuse, neglect, accidents of nature, or
shipping damage. This warranty is in lieu of 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. 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 [phone]. 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 “Declaration of Hazardous Material
and Decontamination” form and comply with the requirements specified in it.
The form is available from our website at
completed form must be either emailed to [e-mail]
435-750-9579. Campbell Scientific will not 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.

www.campbellsci.com/repair

. A

or faxed to

ASPTC Table of Contents

PDF viewers note: These page numbers refer to the printed version of this document. Use
the Adobe Acrobat® bookmarks tab for links to specific sections.

1. General .........................................................................1

1.1 Specifications............................................................................................1

1.2 Power Considerations...............................................................................2

2. Mounting.......................................................................2

3. Programming ...............................................................3

3.1 Absolute Temperature ..............................................................................3

3.1.1 CRBasic ..........................................................................................3

3.1.2 Edlog...............................................................................................4

3.2 Delta Temperature....................................................................................5

4. Maintenance.................................................................8

Figures

2-1. ASPTCs Mounted to Bowen Ratio Arms................................................2

2-2. ASPTC Mounted to the UT018...............................................................2

3-1. Wiring for a Single ASPTC ....................................................................3

3-2. Wiring for a Pair of ASPTCs ..................................................................6

i

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

1. General

The model ASPTC is an aspirated shield with a chromel-constantan
thermocouple temperature sensor. One ASPTC can be used to measure
absolute air temperature. Two ASPTCs are used to make delta temperature
measurements. The differential voltage thermocouple instruction (TCDiff in
CRBasic or Instruction 14 in Edlog) is recommended to measure the ASPTC,
because a differential measurement reduces noise.

1.1 Specifications

Weight: 1.9 lbs (0.86 kg)

Shield

Material: UV stabilized polyethylene
Dimensions

Length: 21 inch (53.3 cm )
Height: 5.8 inch (14.7 cm)
Large Outer Diameter: 2.3 inch (5.8 cm)
Small Outer Diameter: 1.8 inch (4.6 cm)

Fan

Air Velocity at
Thermocouple: 5.5 m/s @ 12 Vdc

Life Expectancy: 65,000 hrs @ 30°C
Current Drain: 260 mA @ 12 Vdc
Operating Voltage: 9 to 13 Vdc
Operating Temperature: -10° to 70°C
Reverse Polarity Protected

Thermocouple

Type: Chromel-Constantan
Diameter: 0.003 inch (0.0762 mm)
Typical Output: 60 μV/°C
Accuracy: Refer to the “Thermocouple Measurement”

section in your datalogger manual.

1

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

1.2 Power Considerations

The ASPTC should be powered by an external 12 VDC deep cycle, battery
with an SP20R solar panel or the PS100 with the AC charger. A PS100 with a
solar panel will not have enough reserve power for overcast days.

2. Mounting

The ASPTC can be mounted on the Campbell Scientific's Bowen Ratio arms
(see Figure 2-1) or UT018 crossarm (see Figure 2-2).

When using the Bowen Ratio arms to mount the ASPTC, mount it to the side
of the arm such that the ASPTC intake is at the same height as the water vapor
intake.

The ASPTC may also be mounted on a user supplied crossarm with a square
cross section (1.5 in. x 1.5 in.).

2

FIGURE 2-1. ASPTCs Mounted to Bowen Ratio Arms

FIGURE 2-2. ASPTC Mounted to the UT018

3. Programming

3.1 Absolute Temperature

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

The ASPTC is wired to the datalogger as shown in Figure 3-1.

3.1.1 CRBasic

CRBasic is provided in our LoggerNet, PC400, and RTDAQ datalogger
support software. Dataloggers that are programmed with CRBasic include our
CR800, CR850, CR1000, CR3000, CR5000, and CR9000(X). These
dataloggers use the TCDiff instruction to measure the ASPTC.

A reference temperature measurement is required. To provide this
measurement, a thermistor is built into the wiring panel of our CR800, CR850,
CR1000, CR30000, and CR5000 dataloggers. The PanelTemp instruction is
used to measure the datalogger’s built in thermistor. For the CR9000(X), a
PRT is built into the CR9050 and CR9051E input modules. The ModuleTemp
instruction measures the CR9050 or CR9051E’s built in PRT.

The terminal strip cover should always be installed on the datalogger wiring
panel when measuring thermocouples.

or AG

CLEAR

FIGURE 3-1. Wiring for a Single ASPTC

NOTE

For a detailed discussion on thermocouple measurements, see the
Measurement Section of the datalogger manuals.

3

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

EXAMPLE 1. Sample CR1000 program for measuring Absolute
Temperature with ASPTC

'CR1000
'Declare Variables and Units

Public PTemp_C
Public Temp_C
Units PTemp_C=Deg C
Units Temp_C=Deg C

'Define Data Tables

DataTable(Table1,True,-1)
DataInterval(0,60,Min,10)
Average(1,Temp_C,FP2,False)
EndTable

'Main Program

BeginProg
Scan(1,Sec,1,0)

'Wiring Panel Temperature measurement PTemp_C

PanelTemp(PTemp_C,_60Hz)

'Type E (chromel-constantan) Thermocouple measurements Temp_C

TCDiff(Temp_C,1,mV2_5C,1,TypeE,PTemp_C,True,0,_60Hz,1,0)

'Call Data Tables and Store Data

CallTable(Table1)
NextScan
EndProg

3.1.2 Edlog

NOTE

Edlog is provided in our LoggerNet and PC400 datalogger support software.
Dataloggers that are programmed with Edlog include our CR7, CR10(X),
CR23X, and 21X. These dataloggers use Instruction 11 to measure the
ASPTC. A reference temperature measurement is required.

The temperature of the datalogger wiring panel is used as the reference
temperature for the thermocouple measurement. The CR10(X) panel
temperature is measured with the CR10TCR using Instruction 11. The CR23X
and 21X panel temperature is found using Instruction 17. The 21X panel
temperature thermistor is located under differential input channel 4. Wiring
the ASPTC into differential channel 4 reduces potential error caused by
temperature gradients on the terminal strip. For the CR7, a PRT is included in
the CR723T input card. This built-in PRT is measured with Instruction 17.
The terminal strip cover should always be installed on the datalogger wiring
panel when measuring thermocouples.

For a detailed discussion on thermocouple measurements, see the
Measurement Section of the datalogger manuals.

4

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

EXAMPLE 2. Sample CR10(X) Instructions for measuring Absolute
Temperature with ASPTC

1: Temp (107) (P11)*
1: 1 Reps
2: 1 SE Channel
3: 3 Excite all reps w/E3
4: 1** Loc [ CR10TCR_C ]
5: 1 Mult
6: 0 Offset

CAUTION: The CR10TCR reference temperature must be in degrees Celsius when used in
Instruction 14.

2: Thermocouple Temp (DIFF) (P14)
1: 1 Reps
2: 21† ± 2.5 mV 60 Hz Rejection Range
3: 6*** DIFF Channel
4: 2 Type E (Chromel-Constantan)
5: 1** Ref Temp Loc [ CR10TCR_C ]
6: 2** Loc [ ASPTC_C ]
7: 1‡ Mult
8: 0‡ Offset

* Instruction 17 is used to find the
panel temperature on a 21X.
** Proper entries will vary depending on the program.
*** Differential input channel 4 on the 21X.

† On the 21X the 5 mV slow input range is used.
‡ For degrees Fahrenheit use a Mult of 1.8 and Offset of 32.

3.2 Delta Temperature

Delta temperature can be measured with two ASPTCs. Wire them as shown in
Figure 3-2. A voltage is induced between the lower and upper ASPTC and is
directly related to the difference in temperature at those two levels. There is no
inherent sensor offset error. The delta temperature is then measured directly
with the TCDiff or Instruction 14. The temperature of the lower ASPTC is
used as the reference for the differential thermocouple measurement.

If the accuracy of the absolute temperature at both the lower and upper ASPTC
is a concern, measure both ASPTCs with TCDiff or Instruction 14 (differential
voltage thermocouple measurement) as outlined in Section 3.1. To find the
delta temperature, simply subtract the upper temperature from the lower one.

If the 21X is used to power the fans (or any other 12 VDC sensor) the current
drawn by the fans may cause a difference in ground potential between the 21X
ground terminals and the reference ground point in the datalogger. This
ground potential difference results in an offset on single ended measurements.
In thermocouple measurements this offset can translate to as much as ±1°C.
This offset does not affect differential measurements, thus, the delta
temperature is not affected.

5

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

AG or GND

FIGURE 3-2. Wiring for a Pair of ASPTCs

6

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

EXAMPLE 3. Sample CR1000 program for measuring Temperature
Gradient with the ASPTC

'CR1000
'Declare Variables and Units

Public PTemp_C
Public AirTemp(2)
Alias AirTemp(1)=Temp_C_1
Alias AirTemp(2)=Temp_C_2
Public Delta_Temp_C
Units PTemp_C=Deg C
Units AirTemp=Deg C
Units Delta_Temp_C=Deg C

'Define Data Tables

DataTable(Table1,True,-1)
DataInterval(0,60,Min,10)
Average(1,Temp_C_1,FP2,False)
Average(1,Temp_C_2,FP2,False)
Average(1,Delta_Temp_C,FP2,False)
EndTable

'Main Program

BeginProg
Scan(1,Sec,1,0)

'Wiring Panel Temperature measurement PTemp_C

PanelTemp(PTemp_C,_60Hz)

'Type E (chromel-constantan) Thermocouple measurements Temp_C

TCDiff(Temp_C_1,2,mV2_5C,1,TypeE,PTemp_C,True,0,_60Hz,1,0)
Delta_Temp_C=Temp_C_1-Temp_C_2

'Call Data Tables and Store Data

CallTable(Table1)
NextScan
EndProg

7

Model ASPTC Aspirated Shield with Fine Wire Thermocouple

EXAMPLE 4. Sample CR10(X) Instructions for Measuring Temperature
Gradient with the ASPTC

1: Temp (107) (P11)*
1: 1 Reps
2: 1 SE Channel
3: 3 Excite all reps w/E3
4: 1** Loc [ CR10TCR_C ]
5: 1 Mult
6: 0 Offset

2: Thermocouple Temp (SE) (P13)
1: 1 Reps
2: 21† ± 2.5 mV 60 Hz Rejection Range
3: 12*** SE Channel
4: 2 Type E (Chromel-Constantan)
5: 1** Ref Temp Loc [ CR10TCR_C ]
6: 2** Loc [ ASP_LWR ]
7: 1 Mult
8: 0 Offset

CAUTION: The CR10TCR reference temperature must be in degrees Celsius when used in
Instruction 14.

3: Thermocouple Temp (DIFF) (P14)
1: 1 Reps
2: 21† ± 2.5 mV 60 Hz Rejection Range
3: 6*** DIFF Channel
4: 2 Type E (Chromel-Constantan)
5: 2** Ref Temp Loc [ ASP_LWR ]
6: 3** Loc [ ASP_UPR ]
7: 1‡ Mult
8: 0‡ Offset

4: Z=X-Y (P35)
1: 2** X Loc [ ASP_LWR ]
2: 3** Y Loc [ ASP_UPR ]
3: 4** Z Loc [ del_ASP ]

* Instruction 17 is used to find the
panel temperature on a 21X.
** Proper entries will vary depending on the program.
*** Single ended input channel 8 and
differential input channel 4 on the 21X.

† On the 21X the 5 mV slow input range is used.
‡ For degrees Fahrenheit use a Mult of 1.8 and Offset of 32.

4. Maintenance

8

Keep the intake and thermocouple free from debris. Debris can be blown away
with a can of compressed air. Tweezers may also be used to pick the debris
from the thermocouple. Be careful not to damage the junction.

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