Embed Size (px)
Citation preview
♦ PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
Email: [email protected]: (516) 334-5959 • FAX: (516) 334-5988
www.ietlabs.comIET LABS, INC.
SR-100 / SR-100DCSR-102 / SR-102DCSR-103 / SR-103DCSR-104 / SR-104DC
Copyright © 2014 IET Labs, Inc.Visit www.ietlabs.com for manual revision updates
SR Series im/July 2014
♦ PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
Email: [email protected]: (516) 334-5959 • FAX: (516) 334-5988
www.ietlabs.comIET LABS, INC.
WARRANTY
We warrant that this product is free from defects in material and workmanship and, when properly used, will perform in accordance with applicable IET specifi cations. If within one year after original shipment, it is found not to meet this standard, it will be repaired or, at the option of IET, replaced at no charge when returned to IET. Changes in this product not approved by IET or application of voltages or currents greater than those allowed by the specifi cations shall void this warranty. IET shall not be liable for any indirect, special, or consequential damages, even if notice has been given to the possibility of such damages.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.
i
WARNING
OBSERVE ALL SAFETY RULESWHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES.
Dangerous voltages may be present inside this instrument. Do not open the caseRefer servicing to qualifi ed personnel
HIGH VOLTAGES MAY BE PRESENT AT THE TERMINALS OF THIS INSTRUMENT
WHENEVER HAZARDOUS VOLTAGES (> 45 V) ARE USED, TAKE ALL MEASURES TOAVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS.
USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARECONDUCTORS WHEN USING THIS INSTRUMENT.
Use extreme caution when working with bare conductors or bus bars.
WHEN WORKING WITH HIGH VOLTAGES, POST WARNING SIGNS AND KEEP UNREQUIRED PERSONNEL SAFELY AWAY.
CAUTION
DO NOT APPLY ANY VOLTAGES OR CURRENTS TO THE TERMINALS OF THISINSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON
THE FRONT PANEL OR THE OPERATING GUIDE LABEL.
ii
ContentsChapter 1 Introduction ..............................................................................1
1.1 Introduction ........................................................................................................... 1
1.2 Deleted Case (DC) option ..................................................................................... 2
Chapter 2 Specifi cations ...........................................................................3
Specifi cations ................................................................................................................ 3
Chapter 3 Operation ..................................................................................6
3.1 Self-Heating .......................................................................................................... 6
3.2 Temperature compensation ................................................................................... 6
3.2.1 Temperature sensor ..................................................................................... 6
3.2.2 Connection to the temperature sensor ......................................................... 6
3.2.3 Calculating the correction ........................................................................... 7
3.3 Schematic Layouts ................................................................................................ 8
3.4 Calibrating secondary Resistance Standards ........................................................ 8
3.5 Bridge connections ................................................................................................ 9
3.5.1 Wheatstone Bridge ...................................................................................... 9
3.5.2 Kelvin Bridges ............................................................................................ 10
iii
Figures and TablesFigure 1-1: SR Series Transportable Resistance Standard .......................1
Figure 2-1: Temperature coeffi cient comparison .........................................4
Figure 2-2: Typical Operating Guide affi xed to unit ......................................5
Table 3-1: Voltage and power limits .............................................................6
Figure 3-1: Sample temperature correction chart .......................................7
Figure 3-2: SR-100 schematic diagram for test connections .......................8
Figure 3-3: SR-102 schematic diagram for test connections .......................8
Figure 3-4: SR-103 schematic diagram for test connections .......................8
Figure 3-5: SR-104 schematic diagram for test connections .......................8
Figure 3-6: Wheatstone bridge connections ................................................9
Figure 3-7: Kelvin bridge connections .........................................................10
Figure 3-8: Model 242D Resistance-Measuring System Connection ..........10
iv
1
SR-102/SR-103/SR-104
1Introduction
Chapter 1
INTRODUCTION
1.1 Introduction
The SR-100, SR-102, SR-103, and SR-104 Series of Transportable Resistance Standards are at a perfor-mance grade just under national laboratory standards. They are 1 Ω, 100 Ω, 1 kΩ, and 10 kΩ resistance standards that have historically been shown to be pre-eminent in accuracy, stability, and temperature coeffi cient performance. See Figure 1-1.
Figure 1-1: SR Series Transportable Resistance Standard
The SR Series offer an extremely low temperature coeffi cient of less than 0.1 ppm/°C, and power coef-fi cient of less than 1 ppm/W. These characteristics facilitate precise laboratory comparisons without critical environmental controls.
For maximum accuracy, these standards offer a temperature-correction chart and a built-in RTD temperature sensor to determine internal temperature and make a precise correction.
These resistance standards are designed as totally transportable bench top instruments. They are pro-tected against shock caused by temperature and pres-sure gradients because they are sealed in a mechani-cally reinforced, oil-fi lled container. This makes it possible for these standards to be transported from one region to another or through varying altitudes.
To eliminate lead-resistance, contact-resistance, and leakage-resistance effects, all versions have a fi ve-terminal resistor confi guration. The four resistor terminals are gold-plated tellurium-copper. This al-lows fi ve-terminal measurements that further reduce external resistance.
Accurate resistance levels ranging from 0.1 Ω to 100 MΩ can be established using a combination of the SR Series resistance standard, a transfer bridge, and transfer standards such as IET’s SR-1010, SR-1030, SR-1050, and SR-1060.
2
SR-102/SR-103/SR-104
2 Introduction
1.2 Deleted Case (DC) option(SR-100/DC,SR-102/DC, SR-103/DC, SR-103/
DC)
The deleted case (DC) option can further enhance the stability of the resistance standard. It is specifi -cally designed for oil-bath operation. This version comes without the external case, but it retains the fi ve-terminal connection to the resistor.
When the standards are used in an oil bath, the re-sistance elements maintain a constant temperature, providing outstanding short-term stability, which is especially important when making Quantum Hall Effect measurements.
3
SR-102/SR-103/SR-104
3Specifi cations
Chapter 2
SPECIFICATIONS
For the convenience of the user, pertinent specifi cations are given in a typical OPERATING GUIDE affi xed to the case of the instrument, such as the one shown in Figure 2-2.
SPECIFICATIONS
Value Model Number1 Ω SR100
100 Ω SR102
1,000 Ω SR103
10,000 Ω SR104
Stability (SR102, 103, 104)First 2 years: ±1 ppm/yearThereafter: ±0.5 ppm/year
Temperature coeffi cientTemperature coeffi cient (α): <0.1 ppm/°C at 23°C1/2 rate of TC change (β): <0.03 ppm/°C from 18°C to 28°Cα and β are determined by the following expression:
RS=R23[1+α23(t-23)+ß(t-23)2]where RS = Standard Resistance at temperature tNo ovens or external power required
Power coeffi cient<1 ppm/W
Adjustment to nominal
Model Adjustment to nominal
SR100 ±10 ppm
SR102, 103, 104 ±1 ppm
Max voltage500 V peak to case
Power rating1 W (Momentary 100 W overloads will not cause failure)
Insulation resistanceAll terminals maintain a minimum 1012 Ω to ground
Internal temperature sensor100 Ω, 1 k Ω, or 10 kΩ resistor with 1,000 ppm/°C temperature coeffi cient.Integral thermometer well is provided for calibration
Hermetic sealingTo eliminate the effects of humidity, the resistor is hermetically sealed in oil with metal-to-glass seals. The resistance changes <±0.1 ppm with normal atmospheric pressure and humidity changes.
Pressure effectsNo pressure effects under normal atmospheric changes. As an actual historical case, measurements taken at NIST in Gaithersburg, MD (sea-level) will be consistent with measurements taken at NIST in Boulder, CO (1,600 m above sea-level).
Connection terminalsFive-terminal construction, four-terminal resistor with ground intercept for the standard and temperature resistor.
Thermal emfThermal emf at the terminals does not exceed±0.1 μV under normal conditions.
Thermal laggingThermal lagging time constant is 1 hour minimum (1-1/e of total change in one hour).
4
SR-102/SR-103/SR-104
4 Specifi cations
Dielectric soakage effectThe resistance stabilizes to within 0.1 ppm of fi nal value within 5 seconds with 1 V applied to the resistor.
Current reversalWith the reversal of the current through the resistor, the resistance value changes less than ±0.1 ppm.
PackagingThe units are mounted in a sturdy formica-veneered wooden case which has a removable lid with a carrying handle. Calibration and other data is attached to the inside of the lid.
Typical performance:
Figure 2-1: Temperature coeffi cient comparison between a typical SR-102 unit
and a typical 100 Ω resistance standard
Shock effectsThe resistance changes is <0.2 ppm when subjected to 2 drops three-foot drops to a concrete fl oor on each of the 3 mutually perpendicular faces (6 drops total).
DimensionsRegular25.4 cm x 20.6 cm x 31.1 cm (10” x 8.1” x 12.25”)Deleted case (DC) version12.7 cm x 8.9 cm x 17.8 cm (5.0” x 3.5” x 7.0”)
WeightRegular4.8 kg (10.5 lb)Deleted case (DC) version1.8 kg (4.0 lb)
Each unit includes:• Built-in temperature sensor• Temperature correction chart• Instruction manual• A2LA accredited ISO/IEC17025 calibration
certifi cate
5
SR-102/SR-103/SR-104
5Specifi cations
Fig
ure
2-2
: Ty
pic
al O
per
atin
g G
uid
e af
fi xe
d t
o u
nit
Appr
oxim
ate
Tem
pera
ture
(°C
)
-3
-2.5-2
-1.5-1
-0.50
0.51 -0
.5%
-0.4
%
-
0.3%
-0.2
%
-
0.1%
0
.0%
0
.1%
0.
2%
0.3%
0.
4%
0.
5%
SR
104
RE
SIS
TAN
CE
STA
ND
AR
DC
ON
SU
LT IN
ST
RU
CT
ION
MA
NU
AL
FO
R P
RO
PE
R IN
ST
RU
ME
NT
OP
ER
AT
ION
No
min
al V
alu
e: 1
0 kΩ
Po
wer
Rat
ing
: 1
W; m
omen
tary
100
W o
verlo
ads
w
ill no
t cau
se fa
ilure
.
Sta
bili
ty:
±1 p
pm/ y
ear,
first
2 y
ears
.
± 0
.5 p
pm/y
ear t
here
afte
r.
Bre
akd
ow
n V
olt
age:
500
V p
eak
to c
ase.
Po
wer
Co
effi
cien
t: <
1 pp
m/W
For
cor
rect
ed r
esis
tanc
e at
oth
er t
empe
ratu
res,
see
char
t or
gra
ph o
r ca
lcul
ate
as f
ollo
ws:
RS =
R23
[ 1
+ αααα α
23
23
23
23
23(((( (t
−2
3)
+ β
(−
23
) +
β(
−2
3)
+ β
(−
23
) +
β(
−2
3)
+ β
(t−
23
)−
23
)−
23
)−
23
)−
23
)2222 2]]]] ]
Wh
ere
Rs
= S
tan
dar
d R
esis
tan
ce a
t te
mp
erat
ure
t
R23
(re
sist
ance
at 2
3.0
°C)=
10.
000
001
4 k ΩΩΩΩ Ω
(Dev
. fro
m n
omin
al v
alue
= 0.
14
ppm
at
23.0
°C
)
αααα α2
3 =
0.1
ppm
/°C
ββββ β=
-0.0
26 p
pm/°
C²
T =
Act
ual t
empe
ratu
re a
s de
term
ined
by
wel
l th
erm
omet
er o
r fr
omTe
mpe
ratu
re S
enso
r m
easu
red
resi
stan
ce (R
T)
Whe
re R
T is
the
resi
stan
ce o
f Tem
pera
ture
Sen
sor
at
tem
pera
ture
T
RT2
3 (s
enso
r re
sist
ance
at 2
3.0
°C)=
10.
000
10 k
ΩΩΩΩ Ω
(Dev
iatio
n fr
om n
omin
al v
alue
=
+0.0
01%
at
23.0
°C
)
Resistance of standard expressed as differencefrom 23° value (10 kohms + 0.14 ppm)
Tem
per
atu
re o
f st
and
ard
res
isto
r ex
pre
ssed
as
per
cen
tag
e ch
ang
e o
f Te
mp
erat
ure
Sen
sor
Res
ista
nce
(RT)
at
tem
pera
ture
T f
rom
(R
T23)
10.
000
10 k
ΩΩΩΩ Ω.
e.g.
if
RT
= 10
.010
1 i
s 0.
1% a
bove
RT2
3, th
e re
sist
ance
of
the
stan
dard
=
10.0
10 1
0 k ΩΩΩΩ Ω
.(m
ay a
lso
be
ob
tain
ed f
rom
th
e fo
rmu
la o
r th
e te
mp
erat
ure
ch
art)
Mo
del
: SR
-104
SN
: J
1-08
2460
3
By:
JOS
Dat
e: 1
6-O
ct-2
008
His
tory
of
Sta
nd
ard
Dev
iati
on
(p
pm
)
Te
mp
.(º
C)
Re
s.
(k)
De
v.
fro
m
No
min
al(p
pm
)
18.0
9.99
998
99
-1.0
118
.59.
99 9
99 1
6-0
.84
19.0
9.99
999
32
-0.6
819
.59.
99 9
99 4
7-0
.53
20.0
9.99
999
61
-0.3
920
.59.
99 9
99 7
3-0
.27
21.0
9.99
999
84
-0.1
621
.59.
99 9
99 9
3-0
.07
22.0
10.0
0 00
0 01
0.01
22.5
10.0
0 00
0 08
0.08
23.0
10.0
0 00
0 14
0.14
23.5
10.0
0 00
0 18
0.18
24.0
10.0
0 00
0 21
0.21
24.5
10.0
0 00
0 23
0.23
25.0
10.0
0 00
0 24
0.24
25.5
10.0
0 00
0 23
0.23
26.0
10.0
0 00
0 21
0.21
26.5
10.0
0 00
0 17
0.17
27.0
10.0
0 00
0 12
0.12
27.5
10.0
0 00
0 06
0.06
28.0
9.99
999
99
-0.0
1T
=(
x
103 +
23)
°CR
T - R
T23
RT2
3
IET
LA
BS,
IN
C.
CA
GE
CO
DE
: 62
015
w
ww
.ietl
abs.
com
form
erly
man
ufac
ture
d by
534
Mai
n S
tree
t, W
estb
ury,
NY
115
90(8
00)
475-
1211
•
(51
6) 3
34-5
959
• F
ax:
(516
) 33
4-59
88
WA
RN
ING
Obs
erve
all s
afet
y rul
es w
hen
wor
king
with
hig
h vo
ltage
s or li
ne vo
ltage
s. C
onne
ct th
e (G
) ter
min
al to
ear
th g
roun
d in
ord
er to
mai
ntai
n th
e ca
se a
t a sa
fe vo
ltage
. Whe
neve
r haz
ardo
us vo
ltage
s (>4
5 V
) are
use
d, ta
ke a
ll mea
sure
s to
avoi
d ac
cide
ntal
cont
act w
ith a
ny liv
e co
mpo
nent
s: a
) Use
max
imum
insu
latio
n an
d m
inim
ize
the
use
of b
are
cond
ucto
rs. b
) Rem
ove
pow
er w
hen
adju
stin
g sw
itche
s. c
) Pos
t war
ning
sig
ns a
nd k
eep
pers
onne
l saf
ely
away
.
SR
104
Labe
l/100
%/0
5-28
-10
10/1
3/20
080.
14
18°C
19°C
20°C
21°C
22°C
23°C
28°C
27°C
26°C
25°C
24°C
6
SR-102/SR-103/SR-104
6 Operation
Chapter 3 OPERATION
3.1 Self-Heating
To minimize self-heating in the bridge or resistor being measured, low power must be used in both the resistance and temperature sensors. Self-heating is generally noticeable by a steady drift in the read-ing while power is being applied. It can be avoided if power is kept below 10 mW in the standard and100 mW in the temperature sensor. Voltage and power limits are given in Table 3-1.
Model ValueResistance R Sensor RMax
VoltageMax
PowerMax
VoltageMax
PowerSR-100 1 Ω 0.1 V 10 mW 0.1 V 100 mW
SR-102 100 Ω 1 V 10 mW 0.1 V 100 mW
SR-103 1 kΩ 3.16 V 10 mW 10 V 100 mW
SR-104 10 kΩ 10 V 10 mW 1 V 100 mW
Table 3-1: Voltage and power limits
CAUTION
To get accurate readings, keep the power low to avoid overheating the instrument. See instructions below.
3.2 Temperature compensation
3.2.1 Temperature sensor
The temperature sensor resistance network consists of a copper resistor in series with a low temperature coeffi cient resistor. The resistance of the network at 23°C has a temperature coeffi cient of 1,000 ppm (0.1%) per °C.
The temperature sensor is mounted in the same oil-fi lled container as the standard resistor, and thus is at the same temperature. Since the standard resistor and the temperature sensor have the same nominal resistance, they can be measured on the same bridge and at the same settings.
3.2.2 Connection to the temperature sensor
The temperature sensor can be connected to the same bridges in the same manner as the standard resistor. The bridge can be the same one used to measure the standard resistor, but generally the accuracy does not need to be as high.
7
SR-102/SR-103/SR-104
7Operation
3.2.3 Calculating the temperature correction
The temperature correction chart (in the lid of the unit) can be used to correct the resistance of the Transportable Standard Resistor for temperature ef-fects. Figure 3-1 is a sample of the calibration data and correction chart attached to the unit.
The precise 23°C value of the standard is given in location (1). In the example shown in Figure 3-1, the standard resistance is:
R23 (resistance at 23.0 °C) = 10.000 001 4 kΩ
This resistance value may be used as given, if the change in resistance for the temperature range to be encountered is acceptably small. For example, if the temperature variations from a nominal 23°C, found in a usual calibration laboratory environment, are less than ±2°C, this would result in a worst case resistance change of less than -0.3 ppm (0.3 ppm= +0.14 ppm at 23°C less -0.16 ppm at 21°C; see chart (2)). If this is an acceptable change, then no temperature correc-tion is required.
Note: In the following discussion and in Figure 3-1, t = temperature as a variableT = measured or calculated temperature
If temperature-correction of the standard is needed, then the temperature T of the standard must be de-termined. This may be done by using a thermometer placed in the well of the unit. This temperature T may be used in:
• The resistance/temperature curve (3) • The temperature correction chart (2)• The formula (4), where α and β are given,
and T is the thermometer temperature
Using all three methods in the sample shown in Figure 3-1, a temperature t of 22°C would produce the result of:
RS=10.000 000 1
A more precise way of measuring the temperature of the standard is to measure T using the value of the integral RTD temperature sensor resistor. Use the formula (5) to obtain T where RT is the measured resistance of the RTD at the temperature to be de-termined. This temperature may be used as above to correct the resistance of the standard.
Approximate Temperature (°C)
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
-0.5% -0.4% -0.3% -0.2% -0.1% 0.0% 0.1% 0.2% 0.3% 0.4% 0.5%
SR104 RESISTANCE STANDARDCONSULT INSTRUCTION MANUAL FOR PROPER INSTRUMENT OPERATION
Nominal Value: 10 kΩ
Power Rating: 1 W; momentary 100 W overloads will not cause failure.
Stability: ±1 ppm/ year, first 2 years.
± 0.5 ppm/year thereafter.
Breakdown Voltage: 500 V peak to case.
Power Coefficient: <1 ppm/W
For corrected resistance at other temperatures,
see chart or graph or calculate as follows:
RS = R
23 [ 1 + ααααα
2323232323(((((t−23) + β(−23) + β(−23) + β(−23) + β(−23) + β(t−23)−23)−23)−23)−23)22222]]]]]
Where Rs = Standard Resistance at temperature t
R23 (resistance at 23.0 °C)= 10.000 001 4 kΩΩΩΩΩ
(Dev. from nominal value= 0.14 ppm at 23.0 °C)
ααααα23 = 0.1 ppm/°C βββββ = -0.026 ppm/°C²
T = Actual temperature as determined by well thermometer or from
Temperature Sensor measured resistance (RT)
Where RT is the resistance of Temperature Sensor at
temperature T
RT23 (sensor resistance at 23.0 °C)= 10.000 10 kΩΩΩΩΩ
(Deviation from nominal value = +0.001% at 23.0 °C)
Res
ista
nce
of
stan
dar
d e
xpre
ssed
as
dif
fere
nce
from
23°
val
ue (
10 k
ohm
s +
0.14
ppm
)
Temperature of standard resistor expressed as percentage change of TemperatureSensor Resistance (RT) at temperature T from (RT23) 10.000 10 kΩΩΩΩΩ.e.g. if RT = 10.010 1 is 0.1% above RT23, the resistance of the standard = 10.010 10 kΩΩΩΩΩ.(may also be obtained from the formula or the temperature chart)
Model: SR-104 SN: J1-0824603
By: JOS Date: 16-Oct-2008
History of Standard Deviation (ppm)
Temp.(ºC)
Res. (k )
Dev. from
Nominal(ppm)
18.0 9.99 998 99 -1.0118.5 9.99 999 16 -0.8419.0 9.99 999 32 -0.6819.5 9.99 999 47 -0.5320.0 9.99 999 61 -0.3920.5 9.99 999 73 -0.2721.0 9.99 999 84 -0.1621.5 9.99 999 93 -0.0722.0 10.00 000 01 0.0122.5 10.00 000 08 0.0823.0 10.00 000 14 0.1423.5 10.00 000 18 0.1824.0 10.00 000 21 0.2124.5 10.00 000 23 0.2325.0 10.00 000 24 0.2425.5 10.00 000 23 0.2326.0 10.00 000 21 0.2126.5 10.00 000 17 0.1727.0 10.00 000 12 0.1227.5 10.00 000 06 0.0628.0 9.99 999 99 -0.01
T =( x 103 + 23)°CRT - RT23
RT23
IET LABS, INC.CAGE CODE: 62015 www.ietlabs.com
formerly manufactured by 534 Main Street, Westbury, NY 11590(800) 475-1211 • (516) 334-5959 • Fax: (516) 334-5988
WARNING
Observe all safety rules when working with high voltages or line voltages. Connect the (G) terminal to earth ground in order to maintain the case at a safe voltage. Whenever hazardous voltages (>45 V) are used, take all measures to avoid accidental contact with any live components: a) Use maximum insulation and minimize the use of bare conductors. b) Remove power when adjusting switches. c) Post warning signs and keep personnel safely away.
SR104 Label/100%/05-28-10
10/13/20080.14
18°C 19°C 20°C 21°C 22°C 23°C 28°C27°C26°C25°C24°C
12
4
5
3
Figure 3-1: Sample temperature correction chart
8
SR-102/SR-103/SR-104
8 Operation
3.3 Schematic Layouts
Figure 3-2: SR-100 schematic diagram for test connections, viewed from the top of oil-fi lled can
Figure 3-3: SR-102 schematic diagram for test connections, viewed from the top of oil-fi lled can
Figure 3-4: SR-103 schematic diagram for test connections, viewed from the top of oil-fi lled can
1 ΩStandard Resistor
OilTube
Thermowell
Empty
Padder Resistor
100 ΩTemperature sensor
GND GND
Empty
Padder Resistor
1 kΩStandard Resistor
OilTube
Thermowell
Empty
1 kΩTemperature sensor
GND GND
Empty
Padder Resistor
Figure 3-5: SR-104 schematic diagram for test connections, viewed from the top of oil-fi lled can
3.4 Calibrating secondary Resistance Standards
Transportable Resistance Standards are primary standards that establish the resistance levels in the laboratory. Working or secondary standards can be calibrated with these primary standards. Other nec-essary equipment would be a precision bridge and transfer standards.
In order to eliminate errors from leads, contact re-sistance, and leakage resistance, IET recommends using a bridge such as the model 242D Resistance Measuring System. This system uses fi ve-terminal measurements -- combination of four-terminal and three-terminal guarded -- that help eliminate these errors.
Resistance transfer standards consists of at least 10 equal resistors (R) that can be connected in series, parallel, or series-parallel. This results in resistance values that are l0R, R/10, or R. The accuracy of these ratios is within 1 ppm.
Once a resistance level is established on a bridge, transfer standards can calibrate the remaining decades by transferring decades to decades above or below the established level. Using a set of transfer standards, you can establish and verify resistance decades on bridges from 0.1 Ω through 100 MΩ.
10 kΩ
Sta
nd
ard
Res
isto
r
OilTubeThermowell 10 kΩ
Temp
erature sen
sor
GND GND
Empty
Empty
Padder Resistor
Padder Resistor
100 ΩStandard Resistor
OilTube
Thermowell
Empty
Padder Resistor
100 ΩTemperature sensor
GND GND
Empty
Padder Resistor
9
SR-102/SR-103/SR-104
9Operation
For values below 1 MΩ, models SR1030 or SR1010 Transfer Standards are recommended because of the four-terminal connection that preserves accuracy between series and parallel connections.
For values above 1 MΩ, model SR1050 Transfer Standards are recommended .
For details about the application of 242D, SR1010, SR1030, SR1050, or SR1060, consult their respec-tive manuals.
3.5 Bridge connections
A standard resistor can be used either as a interchange standard or as a comparison standard, depending on the type of bridge. An interchange standard is most commonly used because it is either the most accurate, or its accuracy is the easiest to verify. Many bridges have internal standards and can use the standard resis-tor only for interchange comparisons.
3.5.1 Wheatstone Bridge
Wheatsone bridges do not generally have provision for external standards. The connections shown in Figure 3-5 are for typical Wheastone bridges to be used for interchange comparisons.
Other bridges have external standard connections and can be used to compare the ratio of two resistors. The interchange technique in this case uses a tare resistor for the external standard of the comparison bridge. The tare resistor is adjusted so that the bridge reading is correct for the value of the standard resistor and other resistors can be compared to the standard.
Figure 3-6: Wheatstone bridge connections
10
SR-102/SR-103/SR-104
10 Operation
3.5.2 Kelvin Bridges
Many Kelvin bridges can be used for comparison measurements. The connections in the Figure 3-6 show the bridge connected for interchange measurements. The resistor, where optional, is connected to the indicated terminals.
Figure 3-7: Kelvin bridge connections
Figure 3-8: Model 242D Resistance-Measuring System Connection
