B&B Electronics 4 Channel Input Buffer Board SDAIBB User manual

SDAIBB1300 Manual Cover Page
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
4 Channel Input Buffer Board
Model SDAIBB
Document No. SDAIBB1300
This product designed and manufactured in Ottawa, Illinois USA
of domestic and imported parts by
International Headquarters
B&B Electronics Mfg. Co. Inc. USA
707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350
Phone [phone] -- General Fax [phone]
Home Page: www.bb-elec.com
Sales e-mail: [e-mail] -- Fax [phone]
Technical Support e-mail: s[email protected]ec.com -- Fax [phone]
1999 B&B Electronics
August 1999 B&B Electronics RESERVED. No part of this publication may be reproduced or transmitted in
any form or by any means, electronic or mechanical, including photography, recording, or any information
storage and retrieval system without written consent. Information in this manual is subject to change without
notice, and does not represent a commitment on the part of B&B Electronics.
B&B Electronics shall not be liable for incidental or consequential damages resulting from the furnishing,
performance, or use of this manual.
All brand names used in this manual are the registered trademarks of their respective owners. The use of
trademarks or other designations in this publication is for reference purposes only and does not constitute an
endorsement by the trademark holder.

SDAIBB1300 Manual Table of Contents i
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Table of Contents
CHAPTER 1: GENERAL INFORMATION...........................................1
INTRODUCTION .........................................................................................1
SPECIFICATIONS ........................................................................................1
CHAPTER 2: CONNECTIONS...............................................................3
POWER SUPPLY CONNECTIONS .................................................................3
INPUT VOLTAGE CONNECTIONS ................................................................5
OUTPUT VOLTAGE CONNECTIONS.............................................................6
CHAPTER 3: CONFIGURATION..........................................................9
OUTPUT OFFSET........................................................................................9
GAIN SELECTION.......................................................................................9
Maximum Gain...................................................................................11
Gain Resistor Determination .............................................................12
Maximum and Minimum Common Mode Voltage..............................13
Maximum Differential........................................................................14
Example Board Setup.........................................................................15
APPENDIX A: GLOSSARY.................................................................A-1
APPENDIX B: ERROR BUDGET CALCULATIONS......................B-1
IMPORTANT SPECS @ 25°C: .................................................................B-1
ERROR CONTRIBUTIONS THAT CAN BE REMOVED WITH CALIBRATION.B-1
ERROR CONTRIBUTIONS THAT CANNOT BE REMOVED W/CALIBRATIONB-1

SDAIBB1300 Manual 1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Chapter 1: General Information
Introduction
The SDAIBB is a data acquisition module with four input buffers
with selectable gains and selectable output offsets. The gain can be set
from 1 to 1000 with a single resistor change. Gains of 1 and 22.28 are
provided. The output can be offset by the provided 0 V for positive ended
systems, by the provided 2.5 V for plus/minus applications, or by a user
selected amount that is brought in on terminal blocks or solder pads. The
SDAIBB is designed to amplify single ended or differential signals in the
range of –0.15 to +5.0 V into +0.01 to +5.0 V signals that are compatible
with the B&B line of data acquisition products. Sensor and power supply
connections are made through terminal blocks or solder pads. A/D
connections are made through DB25 connectors and are designed to
connect to many of the B&B data acquisition products. All lines on the
DB25 connectors are carried through, allowing boards to be “stacked” for
expanding the number of channels or bringing other lines in or out. Three
SDAIBB boards will fill all 11 channels of the 232SDAxx or 485SDAxx
modules.
Specifications
Number of Channels 4
Gain 1 to 1000
1 and 22.28 provided
Max. Gain Error 0.35%
Max. Gain Drift 25 ppm
Max. Input Offset Voltage 200 µV
Max. Input Offset Voltage Drift 2 µV/°C
Input Impedance 2 GΩ, 2pF
Input Voltage Range
Gain = 1 -0.15 to +5.00 V
Gain > 1 -0.15 to +4.60 V
Output Voltage Range
Gain = 1 0.01 to 5.00 V
Gain > 1 0.01 to 4.95 V

2 SDAIBB1300 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Power Supply
Input Voltage
Single Module 10 to 30 VDC
Three Modules 12 to 30 VDC
Input Current 8 mA max. per Module
Current Draw From Precision 5 V 0.5 mA per board
Max. Current Throughput 1 A
Connections
Analog Input Terminal Blocks/Solder Pads
Analog Output DB25 Male Connector and
DB25 Female Connector
Power Terminal Blocks/Solder Pads
Pins 2 and 7 of the Male
DB25
Environment
Operating Temperature -40 to +85 °C
Storage Temperature -65 to +125 °C
Size 5.6 x 2.75 in.
14x7cm

SDAIBB1300 Manual 3
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Chapter 2: Connections
Power Supply Connections
A single SDAIBB board requires 8 mA at 10 to 30 VDC, and can be
brought directly into the board through terminal blocks or solder pads
marked POWER and GND or passed from another board connected to the
male side of the board. See Figure 1 for a system where the power is
brought directly onto the board. When passing power through from
another board, POWER is carried through on pin 2 and GND is carried
through on pin 7. Powers flows in on the male DB25 connector and out on
the female DB25 connector with a 0.5 VDC drop across the board. This
allows multiple boards to be powered with a single power supply by
cascading them. See Table 4 for a list of B&B data acquisition products
that carry power through on pins 2 and 7. Using these devices, you can
power an entire system with a single power supply as shown in Figure 2.
GAIN
JP4
Port Powered
RS-232
MODULE
I/O PORT
O tta w a , Illin o is 6 1 35 0
DATA ACQUISITION
MODEL 232SDA10
JP9
JP10
R8
1
22.28/
USER
JP3
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
POWER
GND
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
OUT
OFF
GND
IN+
IN-
22.28/U S E R
1
GAIN
JP11
OUT.
OFF.
2.5V
0V
JP2
JP6
R2
TB2 TB4
TB5
JP8
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
JP5
A
B
TB1
C D
TB3
JP7
Power Supply
GAIN
22.28/
USER
1
GAIN 1
22.28/
USER
R1
JP1
R7
Figure 1: Port Powered SDA and Powered Board

4 SDAIBB1300 Manual
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JP2
Board 2
JP9
JP10
22.28/USER
1
JP11
GAIN
JP4
R8
1
JP8
22.28/
USER
OUT.
OFF.
2.5V
0V
TB1
OUT
OFF
GND
IN+
IN-
OUT
OFF
GND
IN+
IN-
GAIN
JP6
R2
TB2
JP5
A
B
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
OUT.
OFF.
2.5V
0V
TB4
TB5
C
D
TB3
JP7
OUT
OFF
GND
IN+
IN-
POWER
GND
OUT.
OFF.
2.5V
0V
R1
JP1
GAIN 1
22.28/
USER
JP3
R7
GAIN
22.28/
USER
1
JP2
Board 1
JP9
JP10
22.28/USER
1
JP11
GAIN
JP4
R8
1
JP8
22.28/
USER
OUT.
OFF.
2.5V
0V
TB1
OUT
OFF
GND
IN+
IN-
OUT
OFF
GND
IN+
IN-
GAIN
JP6
R2
TB2
JP5
A
B
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
OUT.
OFF.
2.5V
0V
TB4
TB5
C
D
TB3
JP7
OUT
OFF
GND
IN+
IN-
POWER
GND
OUT.
OFF.
2.5V
0V
R1
JP1
GAIN 1
22.28/
USER
JP3
R7
GAIN
22.28/
USER
1
Power
Ottawa,Illinois61350
MODULE
DATAACQUISITION
MODEL 232SDA10
RS-232
I/O PORT
JP2
JP9
JP10
22.28/USER
1
JP11
GAIN
JP4
R8
1
JP8
22.28/
USER
OUT.
OFF.
2.5V
0V
TB1
OUT
OFF
GND
IN+
IN-
OUT
OFF
GND
IN+
IN-
GAIN
JP6
R2
TB2
JP5
A
B
OUT
OFF
GND
IN+
IN-
OUT.
OFF.
2.5V
0V
OUT.
OFF.
2.5V
0V
TB4
TB5
C
D
TB3
JP7
OUT
OFF
GND
IN+
IN-
POWER
GND
OUT.
OFF.
2.5V
0V
R1
JP1
GAIN 1
22.28/
USER
JP3
R7
GAIN
22.28/
USER
1
Board 3
Figure 2: Single Power Supply System with 11 Channels Supported

SDAIBB1300 Manual 5
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Input Voltage Connections
The SDAIBB can receive signals in the range of –0.15 to +5 VDC
when set to unity gain, and –0.15 to +3.5 VDC when set to any other gain.
Note: This voltage reading is taken from GND on the SDAIBB to
Input+ and GND to Input- voltages. It is not the differential voltage
from Input- to Input+. Signals are brought into the buffer by terminal
blocks or solder pads. The terminal blocks are labeled Input+, Input-,
GND, and Output Offset. See Figures 3, 4, and 5 for typical input
configurations. The voltage that will be amplified is the reading taken from
Input- to Input+. GND is connected to the ground of the SDAIBB and is
provided for making a common reference for the SDAIBB and the input
device. The Output Offset is an input that shifts the output of the SDAIBB.
This feature is discussed further in Chapter 3, Output Offset.
OUT
OFF
GND
IN+
IN-
Figure 3: Differential Signal with GND
OUT
OFF
GND
IN+
IN-
Signal
GND
Figure 4: Single Ended Signal

6 SDAIBB1300 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Output Voltage Connections
The SDAIBB outputs voltages from +0.1 to +5.0 VDC at unity
gain, and +0.1 to +4.95 VDC at any other gain. All lines are carried
straight through on the DB25 connectors, allowing for the addition of extra
channels by connecting on another board.
The SDAIBB output connections are jumper selectable to line up
with the channels of the B&B line of SDAxx data acquisition devices.
When the 4-position shunt is set to JP9, input buffer A is connected to
channel 0 on pin 8, B is connected to channel 1 on pin 9, C is connected to
channel 2 on pin 10, and buffer D is connected to channel 3 on pin 11.
Setting the 4-position shunt to JP10 connects the buffers to channels 4 to 7
(pins 12, 13, 21, and 22 respectively), and setting the shunt to JP11
connects the buffers to channels 8 to 10 (pins 23 to 25). See Table 1 for a
list of the connections when the jumper is on JP9,
Table 2 for when the jumper is on JP10, and Table 3 for when the
jumper is on JP11. Note: When the 4-position jumper is on JP11,
buffer D is not connected to any pins on the DB25 connector.
For a listing of which modules the SDAIBB can connect to and
which channels are compatible on each module, see Table 4.
OUT
OFF
GND
IN+
IN-
Figure 5: Floating Differential Signal

SDAIBB1300 Manual 7
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Table 1: Connections when the 4-position shunt is on JP9
Pin Connection Pin Connection
1---14---
2 Power 15 ---
3---16---
4---17---
5---18---
6---19---
7GND20 ---
8 A output 21 ---
9 B output 22 ---
10 C output 23 ---
11 D output 24 ---
12 --- 25 ---
13 ---
Table 2: Connections when the 4-position shunt is on JP10
Pin Connection Pin Connection
1 --- 14 ---
2 Power 15 ---
3 --- 16 ---
4 --- 17 ---
5 --- 18 ---
6 --- 19 ---
7GND20 ---
8 --- 21 C output
9 --- 22 D output
10 --- 23 ---
11 --- 24 ---
12 A output 25 ---
13 B output

8 SDAIBB1300 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
To support all 11 channels on the SDAxx modules connect 3
SDAIBBs to the I/O port of the SDAxx as shown in Figure 2 on page 4 and
set one board to JP9, one to JP10, and the last to JP11. This will provide
11 independent buffered inputs.
Table 3: Connections when the 4-position shunt is on JP11
Pin Connection Pin Connection
1 --- 14 ---
2 Power 15 ---
3 --- 16 ---
4 --- 17 ---
5 --- 18 ---
6 --- 19 ---
7GND20 ---
8 --- 21 ---
9 --- 22 ---
10 --- 23 A output
11 --- 24 B output
12 --- 25 C output
13 ---
Table 4: Models Compatible with SDAIBB
Model Channel Select Jumper Connections
Supported
Channels
Supported
Power on
pins 2
and 7
2.5V
Output
Offset
Available
485SDA10 JP9
,
JP10
,
JP11 0-10 Yes Yes
485SDA12 JP9
,
JP10
,
JP11 0-10 Yes Yes
232SDA10 JP9
,
JP10
,
JP11 0-10 Yes Yes
232SDA12 JP9
,
JP10
,
JP11 0-10 Yes Yes
232SPDA JP9 0-3 Yes Yes
232SPDACL JP9 0-3 Yes Yes
485SPDA JP9 0-3 Yes Yes
485SPDACL JP9 0-3 Yes Yes
232OPSDA * 4 and 5 No No
ADIO12 JP9 4-7 No No
ADIO10 JP9 4-7 No No
Set the jumper for any position and use the solder pads on the DB25
connector to bring out connections for channels 4 and 5. The other
channels already have selectable gains.

SDAIBB1300 Manual 9
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Chapter 3: Configuration
Output Offset
The output offset is the amount by which the output is shifted.
Equation 1 shows how the output offset affects the output of the buffer.
The negative output rail will clip any reading that has a negative input
differential unless the buffer’s output offset is raised. For this purpose,
output offsets of 0 V and 2.5 V are individually jumper selectable for each
channel on the SDAIBB when mated with a compatible data acquisition
model. JP5 corresponds to channel A, JP6 corresponds with channel B,
JP7 corresponds with channel C, and JP8 corresponds with channel D.
An output offset of 0 V is always available. See Table 4 for a list
of models that support the 2.5 V output offset. An output offset of 0 V is
used for positive only differentials, and an output offset of 2.5 V provides
the maximum input range for signals that run equally positive and negative.
A different output offset may be brought in on the terminal blocks
with the output offset jumper removed on the corresponding channel.
Gain Selection
The gain is individually selectable on each buffer with a two-
position jumper. Gains of 1 and 22.28 are conveniently provided on the
unit for each buffer. JP1 controls the gain on channel A, JP2 controls B,
JP3 controls C, and JP4 controls D. Unity gain is ideal for eliminating the
impedance mismatch between input devices and the data acquisition
module. Table 5 shows the maximum voltage ranges that can be amplified
by the provided gain of 22.28. To change the gain, leave the jumper in the
User/22.28 gain position, remove the through-hole 4.7 kΩresistor, and
replace it with the appropriate value. See Table 6 for some standard inputs,
gains, and appropriate resistor values to achieve the expected gain.
Equation 1:
()
etOutputOffsGainININVout +−= −+

10 SDAIBB1300 Manual
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Change R1 to change the gain on channel A, R2 to change channel
B, R7 to change channel C, and R8 to change channel D. The following
sections explain how to calculate the gain and gain resistor for other input
ranges.
Table 5: Values for Use with the Provided Gain of 22.28
VCM VDIFF Out Ref 1%
Resistor Calculated Gain Output Range
27.5 mV max +55 mV 0 V 4.7 kΩ22.28 0.01 – 1.23 V
0 V ±52 mV 2.5 V 4.7 kΩ22.28 1.32 - 3.68 V
2.5 V ±110 mV 2.5 V 4.7 kΩ22.28 0.03 - 4.97 V
Table 6: Gains and Resistor Values for Standard Inputs
VCM VDIFF Out
Ref GMAX Closest 1% Resistor Calculated Gain Output Range
5mV max +10 mV 0V 119 866
Ω
116.47 0.01 - 1.16 V
50mV max +100mV 0V 12.8 8.66 k
Ω
12.55 0.01 - 1.25 V
0.5V max +1 V 0V 2.18 86.6 k
Ω
2.15 0.01 - 2.18 V
0V ±10 mV 2.5V 118 866
Ω
116.47 1.34 - 3.66 V
0V ±100 mV 2.5V 11.8 9.31 k
Ω
11.74 1.32 - 3.67 V
2.5V ±10 mV 2.5V 247 412
Ω
243.72 0.06 - 4.94 V
2.5V ±100 mV 2.5V 24.7 4.32 k
Ω
24.15 0.09 - 4.91 V
2.5V ±1 V 2.5V 2.47 69.8 k
Ω
2.43 0.07 - 4.93 V

SDAIBB1300 Manual 11
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Maximum Gain
The maximum gain for a known differential voltage and common
mode voltage can easily be determined using the following set of equations.
Equation 5 calculates the maximum gain based on the positive internal rail
of the amplifier. Equation 6 gives the maximum gain based on the negative
internal rail of the amplifier. Equation 7 calculates the maximum gain
without overflowing the output range of the SDAIBB. The smallest
maximum gain value calculated using these equations is the maximum gain
that may be used.
G is the gain, Vcm is the common mode voltage, and Vdiff is the
differential voltage.
Equation 2:
()
DIFF
CM
MAX V
VV
G−
=4.42
Equation 3:
()
DIFF
cm
V
VV
G59.02
max +
=
Equation 4: InputRange
V
GMAX 94.4
=
Equation 5
(
MAX
Gain =
4
2
Equation 6
(
c
V
Gain 2
max =
Equation 7
GainMAX 9
4
.4
=
Example: Find the maximum allowable gain for a differential voltage of
±10 mV and a common mode voltage of 2.5 V.
From Equation 5:
()
380
01.0 5.24.42 =
−
=
MAX
G
From Equation 6:
()
618
01.0 59.05.22
max =
+
=
G
From Equation 7: 247
02.0
94.4 ==
MAX
G
The minimum value calculated is 247, so the maximum allowable gain is
247.

12 SDAIBB1300 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Gain Resistor Determination
Replacing a single resistor changes the gain on each buffer.
Change R1 to modify the gain on channel A, R2 to change channel B, R7
to change channel C, and R8 to change channel D. Use Equation 8 to
determine the value of the gain resistor to attain a calculated gain. To use
this gain value, place the gain jumper corresponding to the correct channel
in the User/22.28 position. JP1 corresponds to channel A, JP2 corresponds
to channel B, JP3 corresponds to channel C, and JP4 corresponds to
channel D.
RGis the value of the gain resistor in ohms.
Equation 8:
()
1
100 −
Ω
=G
k
RG
Equation 9: G
R
k
GΩ
+= 100
1
Example: Find the appropriate 1% resistor for a maximum gain of 150 and
calculate the actual gain.
From Equation 8:
()
141.671
1150
100000 =
−
=
G
R
The nearest 1% resistor that will produce a gain of 150 or less is 681Ω.
From Equation 9: 8.147
681
100000
1=+=G
The nearest 1% resistor is 681Ωwith a resulting gain of 147.8.

SDAIBB1300 Manual 13
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Maximum and Minimum Common Mode Voltage
If the differential voltage range and desired gain are known, the
maximum and minimum common mode voltage can be determined.
Equation 10 is used to calculate the maximum common mode voltage
knowing the gain and the differential voltage. Equation 11 is used to
calculate the minimum common mode voltage. Remember that when
Input+ or Input- is connected to GND on the SDAIBB the
common mode voltage changes as the differential voltage changes.
Equation 10: 2
4.4 GV VV DIFF
CMMAX ×
−=
Equation 11: 2
590.0 GV VV DIFF
CMMIN ×
+−=
Example: Find the allowable range of the common mode voltage for a
input range of ±100 mV with a gain of 10.
From Equation 10: VVCMMAX 9.3
2101.0
4.4 =
×
−=
From Equation 11: VVCMMIN 09.0
2101.0
590.0 −=
×
+−=
The common mode voltage must be between –0.09 and 3.9 V.

14 SDAIBB1300 Manual
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Maximum Differential
To determine the maximum differential voltage that can be
amplified, the gain and the common mode voltage must be known first.
Using this information, the most positive the differential voltage may be is
calculated using Equation 12. Equation 13 is used to calculate the most
negative that the differential voltage may swing. These two values are still
limited by the maximum allowable swing given by Equation 14.
Example: Find the allowable swing of a signal with a common mode
voltage of 1V with a gain of 50.
From Equation 12:
()
136.0
50 14.42 =
−
=
DIFF
V
From Equation 13:
()
0636.0
50590.012 +
=
DIFF
V
From Equation 14: 0988.0
50
94.4 =≤InputRange
The differential voltage can swing as negative as –0.0636 V and as positive
as 0.136 V. However, this full range cannot be achieved with the same
output offset setting due to the 0.0988 V range from Equation 14. To find
the output offset voltage that allows the lower end of this range, use
Equation 1 with Vout set to 0.01 V.
()
etOutputOffsGININVout +−= −+
Rearranged to calculate the desired output offset it looks like this
GVVetOutputOffs DIFFout ×−=
Substitute in the appropriate values and solve for the output offset.
()
VetOutputOffs 19.3500636.001.0 =×−−=
Equation 12:
()
G
V
VCM
DIFF −
=4.42
Equation 13:
()
G
VV
VCM
DIFF 590.02 +
=
Equation 14: G
V
InputRange 94.4
≤

SDAIBB1300 Manual 15
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Example Board Setup
Figure 6 is an example of one possible configuration for the
SDAIBB without modifying the board. Table 7 lists the setup for each
channel.
Table 7: Setup for Figure 6
Channel Output Pin Gain Output Offset
A 8 22.28 2.5 V
B 9 1 0.0 V
C 10 1 2.5 V
D 11 22.28 0.0 V

16 SDAIBB1300 Manual
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Figure 6
C
A
DB
OUT.
OFF.
2.5V
0V
GAIN 1
22.28/
USER
OUT
OFF
GND
IN+
IN-
OUT
OFF
GND
IN+
IN-
1
22.28/USER
GAIN
OUT
OFF
GND
IN+
IN-
OUT
OFF
GND
IN+
IN-
GAIN
22.28/
USER
1
GAIN
1
22.28/
USER
OUT.
OFF.
2.5V
0V
OUT.
OFF.
2.5V
0V
POWER
GND
R7
JP3
TB3
JP7
TB4
TB5
JP8
JP4
R8
JP10
JP11
JP9
OUT.
OFF.
2.5V
0V
JP2
R2
JP6 TB2
JP5
TB1
JP1
R1

SDAIBB3599 Manual A-1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Appendix A: Glossary
Common Mode Voltage
()
CM
V:The voltage about which a differential
voltage swings. When this is measured on the SDAIBB it is calculated
with all voltage readings taken in reference to GND of the SDAIBB as
()
2
−+ +ININ . Note that when one of the inputs is connected to GND of
the SDAIBB the common mode voltage changes as the differential voltage
changes.
Differential Voltage
()
DIFF
V:The difference in voltage across two points
such as the two leads on a thermocouple. When this is measured on the
SDAIBB it is calculated with all voltage readings taken in reference to
GND of the SDAIBB as −+ −ININ .
Gain
()
G:The amount by which the input is multiplied before it is output.
−+ −
=ININ
V
Gain out
Impedance Mismatch: When the output impedance of sensor is different
enough from the input impedance of the data acquisition device to cause
improper sensor readings.
Negative Input Differential: When the voltage and IN- is higher than the
voltage at IN-. 0≤− −+ ININ
Negative Rail: The lowest possible voltage that can be output. For the
SDAIBB there is a negative rail internal to the buffer and a negative rail on
the output of the buffer.
Positive Rail: The highest possible voltage that can be output. For the
SDAIBB there is a positive rail internal to the buffer and a positive rail on
the output of the buffer.

SDAIBB3599 Manual B-1
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax [phone]
Appendix B: Error Budget Calculations
Important Specs @ 25°C:
V offset in
()
OSI
V200 µV
Voffset out
()
OSO
V1000 µV
I offset
()
OS
I2nA
Gain Error 0.35%
Gain Nonlinearity 50ppm
0.1Hz to 10Hz Noise 3.0µV p-p
CMR 84dB @ 60 Hz
Error Contributions that can be Removed With
Calibration
V
in is the input voltage.
Error Contributions that Cannot be Removed with
Calibration
Equation 15: in
OSO
OSI
OS VG
V
V
V+
=
Equation 16:
in
os
OS V
I
I×
=ImpedanceSensor
Equation 17: ppm3500ErrorGain =
Equation 18: in
CM
VVppm×
=4
ErrorCMR
Equation 19: ppm50tyNonlineariGain =
Equation 20: in
V
nV3000
noise10Hz-0.1Hz =