DEM-XTR501C [ETC]
DEM-XTR501C - DISCONTINUED PRODUCT. No longer recommended for new design. ; DEM - XTR501C - 停产的产品。不再建议用于新设计。
| 型号： | DEM-XTR501C |
| 厂家： | 
ETC |
| 描述： | DEM-XTR501C - DISCONTINUED PRODUCT. No longer recommended for new design.
|
| 文件： | 总4页 (文件大小：74K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
DEM-XTR501C
EVALUATION FIXTURE
DESCRIPTION
FEATURES
The DEM-XTR501C evaluation fixtures are fully as-
sembled and tested printed circuit boards including the
XTR501. By connecting a pellistor catalytic detector
and using 50% LEL of Methane, the performance of
the XTR501 can be evaluated.
● PCB SUITABLE FOR STANDARD
ENCLOSURE
● DUT SUPPLIED WITH BOARD
● OPTIMUM PCB LAYOUT
The evaluation fixture is set up for a 2V bridge voltage
and an input span of 50mV. This is equivalent to the
LEL of Methane. Refer to the “How to Calculate RSET
and RSPAN” section for method of calculating the
necessary settings.
APPLICATIONS
● EVALUATE XTR501 PERFORMANCE
● INCOMING INSPECTION TEST FIXTURE
● EVALUATE PELLISTOR PERFORMANCE
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
© 1996 Burr-Brown Corporation
LI-472
Printed in U.S.A. October, 1996
POWER SUPPLY
of a Wheatstone bridge arrangement. The bridge is balanced
by VR1, giving an output of 4mA at IO on Con 2. The output
of the XTR501 can be converted to a voltage in the range of
1V to 5V corresponding to 4 to 20mA, by SW1. This can be
read on the terminal designated VO on Con 2. The voltage
output is filtered at a nominal 1kHz.
The evaluation fixture operates from a single dc supply in
the range of 12V to 30V. The supply being used should be
capable of delivering 1 amp.
BOARD LAYOUT AND CONNECTIONS
When the sensor is exposed to 2.5% Methane, i. e., midscale,
the output should read 12mA, or 2.5V depending on the
switch position. R2 and VR2 set the span of the unit and can
be adjusted to bring the output to the exact value for midscale.
Refer to Figure 1, PCB Layout and Figure 2, Circuit Diagram
for the connections to the evaluation fixture. The 4-part
connector, Con 1, is for the power supply and current/voltage
out. The connector designations are marked in Figure 1, PCB
Layout. The 5-part connector, Con 2, is for pellistor connec-
tions. The numbers refer to the XTR501 pins as indicated in
Figure 2. The circuit diagram also shows the manner in which
the pellistor can be connected. This is for a 5-wire connection.
For a normal 3-wire connection, connect terminal 15 to
terminal 16, and connect terminal 17 to terminal 11.
DEM-XTR501C
THEORY OF OPERATION
The XTR501 demo board should be used in conjunction
with the XTR501 product data sheet and is designed to
provide an example of a typical application in which the
XTR501 could be used. The demo board also fits into one of
the standard industrial enclosures.
The evaluation fixture is set up for an LEL of Methane, and
the assumption that a VQ21 gas sensor, or equivalent, is
being used. Reference to the accompanying circuit diagram
of this document details the circuit values for this application.
The bridge voltage, recommended by the manufacturer for
the gas sensor, is set by R3 and VR3. When the gas sensor is
connected as shown in the circuit diagram, it forms one side
FIGURE 1. PCB Layout.
L1
470µH
Con 1
VIN
12
Con 2
C1
16
24
23
10µF
15
R4
4.7kΩ
R2
470Ω
Com
18
3
VR1
1kΩ
RSPAN
VR2
100Ω
XTR501
R5
1
4.7kΩ
17
11
22
2
SW1
IO
10
14
R6
1.6kΩ
VO
Pellistor
VR3
5kΩ
R1
249Ω
C2
0.1µF
RSET
R3
20kΩ
FIGURE 2. Circuit Diagram.
®
2
DEM-XTR501C
FIGURE 4. PCB Tracking—Solder Side.
FIGURE 3. PCB Tracking—Component Side.
OPERATING INSTRUCTIONS
HOW TO CALCULATE RSET AND RSPAN
To Calculate RSET
The XTR501 demo board, as supplied, is set up for a LEL
of Methane (5% by volume in air). The gas sensor used was
a VQ21 from EEV Gas Sensors, which requires a 2V supply
from the bridge and gives a 50mV deflection for full scale.
See Figure 5. Point (a) will be maintained as 1.235V.
1.235 50kΩ + R
(
)
VB –1.235
SET
Refer to the “How to Calculate RSET and RSPAN” section for
help in calculating values for the bridge voltage and the span
of the unit.
=
10kΩ
RSET 50kΩ
50kΩ V –1.235
(
)
50kΩ + RSET
B
Connect a 24V dc supply to the demo board by means of the
terminals VIN and Com.
=
10kΩ 1.235
RSET
(
) (
)
Connect a DVM to terminals referred to as 16 and 17 on
Con 1 in the layout diagram, and adjust the voltage by
means of VR3 to 2V.
50kΩ
= 1+
RSET
Switch off the power supply.
5 V –1.235
(
)
–1 =
50kΩ
B
Connect the sensor to the unit as shown in the circuit
diagram, referring to the component layout diagram which
contains the terminal labeling.
1.235
RSET
50kΩ 1.235
) (
(
)
RSET
=
Switch on the power supply.
5 V −1.235 –1.235
(
)
B
Connect the DVM to the IO terminal on Con 2 and adjust
VR1 to read 4mA.
Example:
Expose the sensor to the 2.5% Methane and adjust the IO to
read 12mA by means of VR2.
VB
RSET CALCULATED
1.5
2.0
3.0
4.0
5.0
Open
Do not overexpose the sensor to this level of gas as the
sensor can be poisoned through time.
21.858kΩ
7.891kΩ
4.815kΩ
3.464kΩ
SW1 configures the demo board to produce a voltage or
current output. This can be read on the terminals designated
VO and IO on Con 2 in the layout diagram.
®
3
DEM-XTR501C
To Calculate RSPAN
IO = 0.004 + 0.016
1+ 50kΩ / RSPAN
VIN
10
11
SENSE
+VB
4.94
10kΩ
(a)
50kΩ
X
T
R
5
0
1
For VIN = 10mV and IO = 20mA
SET
+VB
1+ 50kΩ / RSPAN
0.02 = 0.004 + 0.016
0.01
RSET
4.94
1+ 50kΩ / R
(
)
0.016
SPAN
=
0.016 0.01
) (
4.94
(
)
494 = 1+ 50kΩ / RSPAN
SET
FIGURE 5. Internal Circuit +VB
.
50kΩ
RSPAN
=
493
= 101.4
ORDERING INFORMATION
DEM-XTR501C
For Evaluation of the XTR501
i.e.
4.94
VIN
50kΩ
= 1+
RSPAN
50kΩ
RSPAN
=
4.94
–1
VIN
®
4
DEM-XTR501C
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