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| 型號： | AD693AE |
| 廠商： | Analog Devices Inc |
| 文件頁數(shù)： | 11/12頁 |
| 文件大?。?/td> | 0K |
| 描述： | IC SGNL COND 4-20MA TX 20-CLCC |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 類型： | 信號調(diào)節(jié)器 |
| 輸入類型： | 電壓 |
| 輸出類型： | 電壓 |
| 接口： | 3 線 |
| 電流 - 電源： | 20mA |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 20-CLCC |
| 供應(yīng)商設(shè)備封裝： | 20-LCCC |
| 包裝： | 管件 |
AD693
REV. A
–8–
R
E 2 = RD
S
60 mV
1.0024
and RE1 = 412 RE2
Figure 14 shows a scheme for adjusting the modified span and
4 mA offset via RE3 and RE4. The trim procedure is to first
connect both signal inputs to the 6.2 V Reference, set RE4 to
zero and then adjust RE3 so that 4 mA flows in the current loop.
This in effect, creates a divider with the same ratio as the
internal divider that sets the 4 mA zero level (–15 mV with
respect to 6.2 V). As long as the input signal remains zero the
voltage at Pin 12, the zero adjust, will remain at –15 mV with
respect to 6.2 V.
Figure 14. Adjusting for Spans between 60 mV and
100 mV (RE1 and RE2) with Fine-Scale Adjust (RE3 and RE4)
After adjusting RE3 place the desired full scale (S) across the
signal inputs and adjust RE4 so that 20 mA flows in the current
loop. An attenuated portion of the input signal is now added
into the V/I zero to maintain the 75 mV maximum differential.
If there is some small offset at the input to the Signal Amplifier,
it may be necessary to repeat the two adjustments.
LOCAL-POWERED OPERATION FOR 0–20 mA OUTPUT
The AD693 is designed for local-powered, three-wire systems as
well as two-wire loops. All its usual ranges are available in three-
wire operation, and in addition, the 0–20 mA range can be used.
The 0-20 mA convention offers slightly more resolution and
may simplify the loop receiver, two reasons why it is sometimes
preferred.
The arrangement, illustrated in Figure 15, results in a 0–20 mA
transmitter where the precalibrated span is 37.5 mV. Con-
necting P1 to P2 will double the span to 75 mV. Sensor input
and excitation is unchanged from the two-wire mode except for
the 25% increase in span. Many sensors are ratiometric so that
an increase in excitation can be used instead of a span
adjustment.
In the local-powered mode, increases in excitation are made
easier. Voltage compliance at the IIN terminal is also improved;
the loop voltage may be permitted to fall to 6 volts at the
AD693, easing the trade-off between loop voltage and loop
resistance. Note that the load resistor, RL, should meter the
current into Pin 10, IIN, so as not to confuse the loop current
with the local power supply current.
An alternative arrangement, allowing wide range span adjust-
ment between two set ranges, is shown in Figure 13. RS1 and
RS2 are calculated to be 90% of the values determined from the
previous formulae. The smallest value is then placed in series
with the wiper of the 1.5 k
potentiometer shown in the figure.
For example, to adjust the span between 25 mV and 40 mV, RS1
and RS2 are calculated to be 2000 and 800 , respectively.
The smaller value, 800
, is then reduced by 10% to cover the
possible ranges of resistance in the AD693 and that value is put
in place.
Figure 13. Wide Range Span Adjustment
A number of other arrangements can be used to set the span as
long as they are compatible with the pretrimmed noninverting
gain of two. The span adjustment can even include thermistors
or other sensitive elements to compensate the span of a sensor.
In devising your own adjustment scheme, remember that you
should adjust the gain such that the desired span voltage at the
Signal Amplifier input translates to 60 mV at the output. Note
also that the full differential voltage applied to the V/I converter
is 75 mV; in the 4-20 mA mode, –15 mV is applied to the
inverting input (zero pin) by the Divider Network and +60 mV
is applied to the noninverting input by the Signal Amplifier. In
the 0–20 mA mode, the total 75 mV must be applied by the
Signal Amplifier. As a result, the total span voltage will be 25%
larger than that calculated for a 4-20 mA output.
Finally, the external resistance from P2 to 6.2 V should not be
made less than 1 k
unless the voltage reference is loaded to at
least 1.0 mA. (A simple load resistor can be used to meet this
requirement if a low value potentiometer is desired.) In no case
should the resistance from P2 to 6.2 V be less than 200
.
Input Spans Between 60 mV and 100 mV
Input spans of up to 100 mV can be obtained by adding an
offset proportional to the output signal into the zero pin of the
V/I converter. This can be accomplished with two resistors and
adjusted via the optional trim scheme shown in Figure 14. The
resistor divider formed by RE1 and RE2 from the output of the
Signal Amplifier modifies the differential input voltage range
applied to the V/I converter.
In order to determine the fixed resistor values, RE1 and RE2, first
measure the source resistance (RD) of the internal divider network.
This can be accomplished (power supply disconnected) by
measuring the resistance between the 4 mA of offset (Pin 13)
and common (Pin 6) with the 6.2 V reference (Pin 14) connected
to common. The measured value, RD, is then used to calculate
RE1 and RE2 via the following formula:
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| AD693AQ | 功能描述:IC TRANSMITTER 4-20MA 20-CDIP RoHS:否 類別:集成電路 (IC) >> 接口 - 傳感器和探測器接口 系列:- 其它有關(guān)文件:Automotive Product Guide 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:74 系列:- 類型:觸控式傳感器 輸入類型:數(shù)字 輸出類型:數(shù)字 接口:JTAG，串行 電流 - 電源:100µA 安裝類型:表面貼裝 封裝/外殼:20-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:20-TSSOP 包裝:管件 |
| AD693BQ | 制造商:AD 制造商全稱:Analog Devices 功能描述:Loop-Powered 4a??20 mA Sensor Transmitter |
| AD694 | 制造商:AD 制造商全稱:Analog Devices 功能描述:4.20 mA Transmitter |
| AD694_02 | 制造商:AD 制造商全稱:Analog Devices 功能描述:4a??20 mA Transmitter |
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