Low Level Measurements Handbook

More documents

Recommendations

Info

Micro-ohmmeterThe micro-ohmmeter also uses the four-wire ratiometric technique, whichis shown in Figure 1-23. It doesn’t have the internal resistors (R S ), as in theDMM, so all four leads must be connected to make a measurement. Also,the terminals that supply test current to the unknown resistance are labeledSource HI and Source LO.FIGURE 1-23: Micro-ohmmeter Resistance MeasurementRef HIR REFSource HIV REFR 1Ref LOR XR 2Sense HIV SENSESense HIR 3Sense LOSense LOR 4Source LOR X = R REF · VSENSEV REFThe pulsed drive mode, shown in Figure 1-24, allows the microohmmeterto cancel stray offset voltages in the unknown resistance beingmeasured. During the measurement cycle, the voltage across the unknownresistance is measured twice, once with the drive voltage on, and a secondtime with the drive voltage turned off. Any voltage present when the drivevoltage is off represents an offset voltage and will be subtracted from thevoltage measured when the drive voltage is on, providing a more accuratemeasurement of the resistance.The dry circuit test mode, shown in Figure 1-25, adds a resistor acrossthe source terminals to limit the open-circuit voltage to less than 20mV. Thisprevents breakdown of any insulating film in the device being tested andgives a better indication of device performance with low level signals. Themeter must now measure the voltage across this resistor (R SH ), as well as thevoltage across the reference resistor and the unknown resistor. See Section3.3.5 for more information on dry circuit testing.<strong>Low</strong> <strong>Level</strong> DC Measuring Instruments 1-27
FIGURE 1-24:Micro-ohmmeter in Pulse ModeRef HIR REF V REFR 1 Source HIRef LO S 1R 2 Sense HISense HIR X V X V SENSEV OSR 3 Sense LOSense LOR 4Source LOR X = R REF · VSENSE 1 – V SENSE 2V REFwhere V SENSE 1 is measured with S 1 closed, and is equal to V X + V OS , andV SENSE 2 is measured with S 1 open, and is equal to V OS .FIGURE 1-25:Micro-ohmmeter with Dry Circuit OnRef HIR REFV REFR 1Source HIRef LOSense HIR 2Sense HIShunt HIR XV SENSER SHV SHR 3Sense LOShunt LOSense LOR 4Source LOR X =V SENSEV REF V SHR REFR SH1-28 SECTION 1
Page 1 and 2: www.keithley.comLLM6 th EditionLow
Page 4 and 5: TABLE OF C ONTENTSSECTION 1 Low Lev
Page 6 and 7: 3.3 Low Resistance Measurements....
Page 8 and 9: SECTION 1Low Level DCMeasuringInstr
Page 10 and 11: 1.1 IntroductionDC voltage, DC curr
Page 12 and 13: FIGURE 1-3: Typical Digital Multime
Page 14 and 15: Coulombmeter FunctionCurrent integr
Page 16 and 17: 1.3.6 The SourceMeter ® Instrument
Page 18 and 19: TABLE 1-1: Specification Conversion
Page 20 and 21: Transfer StabilityA special case of
Page 22 and 23: FIGURE 1-6: Common Mode NoiseMeasur
Page 24 and 25: FIGURE 1-8: Voltage Amplifier+-V 2A
Page 26 and 27: Picoammeter amplifier gain can be c
Page 28 and 29: Using a small-signal transistor in
Page 30 and 31: FIGURE 1-17: High Resistance Measur
Page 32 and 33: FIGURE 1-20: High Resistance Measur
Page 36 and 37: FIGURE 1-26: Typical Digital Electr
Page 38 and 39: In order to cancel internal offsets
Page 40: Sense circuitry is used to monitor
Page 43 and 44: 2.1 IntroductionAs described in Sec
Page 45 and 46: cause significant loading errors. I
Page 47 and 48: Cable leakage resistance is a commo
Page 49 and 50: FIGURE 2-6: Guarding Leakage Resist
Page 51 and 52: Example: Assume R S = 10GΩ and C S
Page 53 and 54: MaterialTABLE 2-2: Properties of Va
Page 55 and 56: QuartzQuartz has properties similar
Page 57 and 58: FIGURE 2-11: Guarding as Applied to
Page 59 and 60: FIGURE 2-13: Guarding the Leakage R
Page 61 and 62: FIGURE 2-15: Simplified Model of a
Page 63 and 64: time and/or temperature. Zero offse
Page 65 and 66: open-circuited, allow the reading t
Page 67 and 68: to equalize charges and minimize ch
Page 69 and 70: If insulators become contaminated,
Page 71 and 72: The input resistance of a feedback
Page 73 and 74: ence. However, in some cases, shiel
Page 75 and 76: FIGURE 2-27: Feedback Coulombmeter
Page 77 and 78: Advantages of Using a Coulombmeter
Page 79 and 80: FIGURE 2-30: Constant-Voltage Metho
Page 81 and 82: In addition to the voltage drop lim
Page 83 and 84: FIGURE 2-34a: Effects of Cable Resi
Page 85 and 86:
Such devices require extreme care i
Page 87 and 88:
charge will be lost through the zer
Page 89 and 90:
FIGURE 2-40: Proper ConnectionCurre
Page 91 and 92:
Figure 2-43 shows an example of AC
Page 93 and 94:
fering voltage or current. A guard
Page 95 and 96:
esponse is the rise time of the ins
Page 97 and 98:
FIGURE 2-47: Shunt Capacitance Effe
Page 99 and 100:
Resistance Measurements (Constant-C
Page 101 and 102:
FIGURE 2-52: Noise Voltage vs. Band
Page 103 and 104:
Source ResistanceAfter the bandwidt
Page 105 and 106:
a. ConfigurationShieldCenterconduct
Page 107 and 108:
• Shielding and Guarding: The fix
Page 109 and 110:
floating circuits, a second grounde
Page 111 and 112:
3.1 IntroductionLow voltage and low
Page 113 and 114:
Thermoelectric EMFsThermoelectric v
Page 115 and 116:
Reversing Sources to Cancel Thermoe
Page 117 and 118:
quency spectrum of these interferen
Page 119 and 120:
ment is almost entirely determined
Page 121 and 122:
FIGURE 3-9: Low Voltages Generated
Page 123 and 124:
FIGURE 3-11a: Multiple Grounds (Gro
Page 125 and 126:
Common-Mode Reversal ErrorsReversin
Page 127 and 128:
FIGURE 3-14: Two-Wire Resistance Me
Page 129 and 130:
FIGURE 3-16: Canceling Thermoelectr
Page 131 and 132:
Both V A and V B are affected by th
Page 133 and 134:
If using a micro-ohmmeter or DMM to
Page 135 and 136:
FIGURE 3-20: Dry Circuit Testing Us
Page 137 and 138:
SECTION 4Applications
Page 139 and 140:
For timing and integrating applicat
Page 141 and 142:
FIGURE 4-2:Using an Electrometer to
Page 143 and 144:
If current flows, the electrodes wi
Page 145 and 146:
4.3 Low Current Measurement Applica
Page 147 and 148:
DC. The Model 6517A can also be use
Page 149 and 150:
voltage (V DS ) and measures the re
Page 151 and 152:
The Keithley Model 248 High Voltage
Page 153 and 154:
FIGURE 4-16: Ion Collector with Gro
Page 155 and 156:
Figure 4-19 shows a Model 6430 conn
Page 157 and 158:
FIGURE 4-21: SIR Test System to Mea
Page 159 and 160:
FIGURE 4-22: Volume ResistivityElec
Page 161 and 162:
these problems, the Alternating Pol
Page 163 and 164:
FIGURE 4-25: Four-Point Collinear P
Page 165 and 166:
Using two electrometers eliminates
Page 167 and 168:
A plot of this function is shown in
Page 169 and 170:
FIGURE 4-31: van der Pauw Measureme
Page 171 and 172:
Through interactive programming, th
Page 173 and 174:
objects. As discussed in Section 2.
Page 175 and 176:
FIGURE 4-36: Faraday CupOutside Ele
Page 177 and 178:
FIGURE 4-38: Connections for Standa
Page 179 and 180:
FIGURE 4-40: Microcalorimeter with
Page 181 and 182:
Measurement MethodFigure 4-42 illus
Page 183 and 184:
FIGURE 4-43: Using a Nanovoltmeter
Page 185 and 186:
exceed the critical current of the
Page 187 and 188:
equation for V/I. Most materials ha
Page 189 and 190:
FIGURE 4-49: van der Pauw Connectio
Page 191 and 192:
5.1 IntroductionChoosing a specific
Page 193 and 194:
TABLE 5-1a: Low Current/High Resist
Page 195 and 196:
Table 5-1b: Source-Measure Instrume
Page 197 and 198:
Table 5-2: High Speed Power Supplie
Page 199 and 200:
Table 5-3: Connectors, Adapters, an
Page 201 and 202:
Table 5-4: CablesTERMINATIONS LENGT
Page 203 and 204:
Table 5-5: Test Leads and ProbesMOD
Page 205 and 206:
Table 5-6: Switching Cards for the
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
APPENDIX ALow LevelMeasurementTroub
Page 213 and 214:
Measurement Type andTypical Applica
Page 215 and 216:
Proper cable and connector assembly
Page 217 and 218:
APPENDIX CGlossary
Page 219 and 220:
channels. For matrix cards, a chann
Page 221 and 222:
R. Buckminster Fuller. Sometimes ca
Page 223 and 224:
NORMAL-MODE REJECTION RATIO (NMRR).
Page 225 and 226:
SOURCEMETER. A SourceMeter instrume
Page 227 and 228:
APPENDIX DSafetyConsiderations
Page 229 and 230:
The types of product users are:Resp
Page 231 and 232:
are the same. Other components that
Page 233 and 234:
1/f noise, 3-7 to 3-83dB point, 2-5
Page 235 and 236:
Normal mode rejection ratio (NMRR),
Page 237 and 238:
Specifications are subject to chang
Page 239:
Specifications are subject to chang
show all

Low Level Measurements Handbook

Create successful ePaper yourself

Delete template?

Save as template?