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參數(shù)資料
| 型號： | MAX1450 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Low-Cost, 1%-Accurate Signal Conditioner for Piezoresistive Sensors |
| 中文描述： | 低成本、1%精確度信號調(diào)理器，用于壓阻式傳感器 |
| 文件頁數(shù)： | 9/12頁 |
| 文件大小： | 98K |
| 代理商： | MAX1450 |
OFFS ET Calibration
Accomplish offset calibration by applying a voltage to the
OFFSET pin (SOFF determines the polarity of V
OFFSET
).
This voltage is generated by a resistor-divider between
V
DD
and V
SS
(R
OFFA
and R
OFFB
in Figure 4). To calibrate
the offset, set V
OFFSET
to 0 and perform a minimum pres-
sure input reading at room temperature. If the output volt-
age (V
OFFZERO
) is greater than 0.5V, connect SOFF to
V
SS
; if V
OFFZERO
is less than 0.5V, connect SOFF to V
DD
.
Adjust V
OFFSET
until V
OUT
= 0.5V.
Note that the magnitude of V
OFFSET
is directly proportion-
al to the gain of the PGA. Therefore, if the PGA gain
changes after performing the offset calibration, the offset
must be recalibrated.
Linearity Calibration (optional)
Correct pressure linearity by using feedback from the
output voltage (V
OUT
) to ISRC to modulate the current
source. If a bridge current is constant with applied
pressure, sensor linearity remains unaffected. If, with a
constant bridge current, the output voltage is nonlinear
with applied pressure (e.g., increasing faster than the
pressure), use pressure linearity correction to linearize
the output.
Performing linearity corrections through the use of a
transfer function is not practical, since a number of
required system variables cannot easily be measured
with a high enough degree of accuracy. Therefore, use a
simple empirical approach. Figure 5 shows the uncom-
pensated pressure linearity error of a silicon PRT. The
magnitude of this error is usually well below 1% of span.
Curves A, B, C, D, E, and F in Figure 5 represent increas-
ing amounts of linearity error corrections, corresponding
to decreasing values in the resistance of R
LIN
. To correct
pressure linearity errors, use the following equation to
determine the appropriate range for R
LIN
:
where S(p) is the sensitivity linearity error as % best
straight-line fit (BSLF). Ideally, this variable resistor
should be disconnected during temperature error com-
pensation. If this is not possible, set it to the maximum
available value.
First measure the magnitude of the uncorrected error
(R
LIN
= maximum value), then choose an arbitrary
value for R
LIN
(approximately 50% of maximum value).
Measuring the new linearity error establishes a linear
relationship between the amount of linearity correction
and the value of R
LIN
.
Note that if pressure linearity correction is to be per-
formed, it must occur after temperature compensation
is completed. A minor readjustment to the FSO and
OFFSET will be required after linearity correction is per-
formed. If pressure linearity correction is not required,
remove R
LIN
.
Ratiometric Output Configuration
Ratiometric output configuration provides an output that
is proportional to the power-supply voltage. When used
with ratiometric A/D converters, this output provides
digital pressure values independent of supply voltage.
Most automotive and some industrial applications
require ratiometric outputs.
The MAX1450 has been designed to provide a high-
performance ratiometric output with a minimum number
of external components (Figure 4).
S ensor Calibration and
Compensation Example
Calibration and compensation requirements for a sensor
involve conversion of a sensor-specific performance
into a normalized output curve. Table 4 shows an
example of the MAX1450’s capabilities.
A repeatable piezoresistive sensor with an initial offset
of 30mV and FSO of 37.5mV was converted into a com-
pensated transducer (using the piezoresistive sensor
with the MAX1450) with an offset of 0.5V and an FSO of
4.0V. The temperature errors, which were on the order
of -17% for the offset TC and -35% for the FSO TC, were
reduced to about ±1% FSO. The graphs of Figure 6
show the outputs of the uncompensated sensor and the
compensated transducer.
R
R
x R
R
R
x S p
( )
LIN
ISRC
+
STC
ISRC
STC
≈
(
)
2
M
Low-Cost, 1%-Ac c urate S ignal Conditioner for
Piezoresistive S ensors
_______________________________________________________________________________________
9
B
C
D
E
F
PRESSURE
LINEARITY
ERROR
UNCOMPENSATED ERROR
(R
LIN
REMOVED)
OVERCOMPENSATED ERROR
(R
LIN
TOOSMALL)
A
Figure 5. Effect of R
LIN
on Linearity Corrections
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參數(shù)描述 |
|---|---|
| MAX14502AETL+ | 功能描述:接口 - 專用 High speed USB to FS-USB RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
| MAX14502AETL+T | 功能描述:接口 - 專用 High speed USB to FS-USB RoHS:否 制造商:Texas Instruments 產(chǎn)品類型:1080p60 Image Sensor Receiver 工作電源電壓:1.8 V 電源電流:89 mA 最大功率耗散: 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:BGA-59 |
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| MAX14503AEWN+ | 制造商:Maxim Integrated Products 功能描述: |
| MAX14503ETL+ | 制造商:Maxim Integrated Products 功能描述: |
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