Omega 868F, Руководство пользователя

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21
SECTION 6 SPECIFICATIONS
MODEL 868
TEMPERATURE SENSOR TYPE:
Three wire or four wire 100 Ω
platinum RTD (alpha = .00385)
4 WIRE
ACCURACY*
SETTING RANGE RESOLUTION (18 °C TO 28 °C: 1 Year)
200 °F -100.0 °F to 199.9 °F 0.1
±
0.4 °F
-199.9 °F to -100.1°F 0.1
±
1 °F
1100 °F -100 °F to 1100 °F 1
±
2 °F
-360 °F to -101 °F 1
±
4 °F
*ACCURACY:
Three wire accuracy is the same if contact
resistance errors are removed by calibration
of instrument plus probe at 32°F. Includes DIN
43760 (ITS-90) conformity, repeatability,
temperature coefficient (65° to 82°F), time
stability (one year) and errors with up to 50 Ω
of lead resistance (each lead). Excludes probe
errors; however, probe errors around 32°F may
be compensated by an internal adjustment.
REPEATABILITY:
0.2 °F Typical for one week at constant
ambient temperature.
TEMPERATURE COEFFICIENT:
65 °F to 82 °F; included in
accuracy specification. From
14 °F to 65 °F, and 82 °F
to 122 °F: less than ±0.015 °F/°F.
MAXIMUM LEAD RESISTANCE:
(each lead): Four wire: 50 Ω
Three wire: 10 Ω
SENSOR CURRENT:
500 µ A max.
TABLE 5-5
PERFORMANCE VERIFICATION
(continued)
MODEL 869
RESISTANCE ALLOWABLE READING
RANGE °C VALUE (Ω) (18° to 28°C)
630°C 9.9 Ω -221 to -219
200°C 60.26 Ω -100.3 to -99.7
200°C 100.00 Ω -0.3 to +0.3
200°C 138.51 Ω 99.7 to 100.3
200°C 174.01 Ω 194.7 to 195.3
630°C 313.71 Ω 599 to 601
10
4.2.2 Signal Phase
During the signal phase the 4 charged values of voltage are
transfered to other parts of the circuit (refer to simplified Figure 4-4).
The following explanations assume more than one charge transfer has
taken place.
1. C
R
is connected across C
E
and after a sufficient number of
zero and signal phases the voltage on C
E
approaches that
stored on C
R
. That voltage is equal to IR
R
.
2. C
Z
is connected between L
2
and the input of A
1
in a way that
opposes the voltage drop across R
T
and L
4
. Since the voltage
charged on C
Z
is IR
Z
the voltage at the output of A
1
is
[A
1
(I(R
T
+ L
4
) - IR
Z
+ Vos)]
or
A
1
(I(R
T
- R
Z
+ L
4
) + IR
Z
+ Vos)
R
Z
is made to equal the value of R
T
at 0°C. This action
eliminates the offset of R
T
(100Ω at 0°C).
3. C
D
is connected between the output of A
1
and the top of C
D
in such a way that opposes the output of A
1
. The voltage
charge on C
D
is
A
1
(I(R
T
- R
Z
+ L
4
) + Vos) - A
1
(IL
4
+ Vos)
or
A
1
I(R
T
- R
Z
)
4. C
A
is connected between the output of the A
2
network and
the top of C
B
in such a way that opposes the output of A
2
.
The voltage charged on C
B
is
A
1
A
2
(I(R
T
- R
Z
+ L
4
) + Vos) - A
1
A
2
(IL
4
+ Vos)
or
A
1
A
2
I(R
T
- R
Z
)
Due to this two phase measurement Vos and lead resistance
effects are eliminated.
Figure 4-4. Four Wire Signal Phase
9
4.2 FOUR WIRE SIGNAL CONDITIONING
There are two phases necessary to condition the signal for
digitization. Each phase lasts for a period equal to one-half of the
back plane period of the A/D converter. These are called the zero
and signal phase.
4.2.1 Zero Phase
During the zero phase, FETs are switched to configure the circuit
shown in Figure 4-3. The fourth wire adds an additional attenuation
that slightly increases the offset voltage at the input to amplifier A
1
.
1. C
R
is connected across R
R
. The voltage charged on C
R
is
equal to IR
R
.
2. C
Z
is connected across R
Z
. The voltage charge in C
Z
is equal to IR
Z
.
3. The input of A
1
is connected through L
3
. Since, ideally, zero
current flows into A
1
the voltage at the output of A
1
is equal
to [A
1
(IL
4
+ Vos)].
4. C
C
is connected between the output of A
1
and common. The
voltage charged on C
C
is equal to the output voltage of A
1
or [A
1
(IL
4
+ Vos)].
5. C
A
is connected between the output of the A
2
network and
common. The voltage charged on C
A
is equal to the output
voltage of A
1
attentuated by A
2
or [A
1
A
2
(IL
4
+ Vos)].
Figure 4-3. Four Wire Zero Phase
22
SPECIFICATIONS continued
MODEL 869
TEMPERATURE SENSOR TYPE:
Three wire or four wire 100 Ω
platinum RTD (alpha = .00385)
4 WIRE
ACCURACY*
SETTING RANGE RESOLUTION (18 °C TO 28 °C: 1 Year)
200 °C -100.0 °C to 199.9 °C 0.1
±
0.3 °C
-199.9 °C to -100.1 °C 0.1
±
1.5 °C
630 °C -100 °C to 630 °C 1
±
1 °C
-220 °C to -101 °C 1
±
2 °C
*ACCURACY:
Three wire accuracy is the same if contact
resistance errors are removed by calibration
of instrument plus probe at 0°C. Includes DIN
43760 (ITS-90) conformity, repeatability,
temperature coefficient (18° to 28°C), time
stability (one year) and errors with up to 50 Ω
of lead resistance (each lead). Excludes probe
errors; however, probe errors around 0°C may
be compensated by an internal adjustment.
REPEATABILITY:
0.1 °C
ambient temperature.
TEMPERATURE COEFFICIENT:
18° to 28°C; included in
accuracy specification. From
-10° to 18°C, and 28° to
50°C: less than ±0.015°C/°C.
MAXI
MUM LEAD RESISTANCE:
(each lead): Four wire: 50 Ω
Three wire: 10 Ω
SENSOR CURRENT:
500 µ A max.
MODELS 868 AND 869
GENERAL SPECIFICATIONS:
DISPLAY:
3
1
/
2
digit LCD, 0.5" (13 mm) height. Polarity and deci-
mal point indication
.
CONVERSION RATE:
1.5 readings per second.
OVERRANGE AND OPEN
SENSOR INDICATION:
Typical for one week at constant