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Instruction Manual
Model 160B
Digital Multimeter
Contains Operating and Servicing Information
for Model 160B Digital Multimeter and
Model 1602B Digital Output
01975, Fourth Printing, December 1977
Keithley Instruments, Inc.
Instrument Division
Cleveland, Ohio, U.S.A.
INSTRUCTION MANUAL
MODEL 1606
DIGITAL MULTIMETER
(AND MODEL 16028 DIGITAL OUTPUT)
@COPYRIGHT 1975, KEITHLEY INSTRUMENTS, INC.
FOURTH PRINTING, DECEMBER 1977, CLEVELAND, OHIO, U.S.A.
CONTENTS :,OOEL ibOJ
CONTENTS
-
SECTION PAGE
SPECIFICATIONS. . "
I. GENERAL INFORMATION. ...... I
I-l, ,NTROD"CT,ON ........ .. I
i-2. FEATURES I
l-3. WARRANTY lNFORHATlON. ............ \
l-4. CHANGE NOTlCE ................ I
l-5. OPTIONAL MODEL 16028 D,G,TAL o"TP" T. ..... I
1-6. OPTIONAL MODEL 1688~ RECHARGEABLE BATTERY PACK
2. INITIAL PREPARATlON ................ k
2-l. GENERAL ...................
2-2. INSPECTlON. ................. .. 2
Z-1. PREPARATION FOR "SE 6
3. OPERATlNG INSTRUCTIONS . . .
3-l. GENERAL 8"
3-2. HOW TO SELECT POWER. . 8
3-3. HOW TO MAKE INPUT CONNECTION!
3-4. HOW TO SELECT FUNCTlON . 8"
3-5. HOW TO MEASURE VOLTAGE 9
3-b. HOW TO MEASURE RESISTANCE. IO
3-7. HOW TO MEASURE CURRENT . I . Ii
3-8. NOISE CONSIOERATIONS .
. . . 12
3-9. THER"AL EHFS . . 12
3-10. MAGNETIC FlELDS . . . 12
3-11. AC ELECTRlC FIELDS . * 12
3-12. SHIELDING. . 12
3-13. HOW TO "SE THE ANALOG OUTPUT 14
3-14. HOW TO USE MODEL 1608 OFF-GROUND . . 14
3-15. HOW TO USE MODEL 16028 DlGlTAL OUTPUT. 16
3-16. HOW TO RACK MOUNT THE MODEL 1608 22
4 THEORY OF OPERATION. . . . . . . . . : : . . 23
4-l. GENERAL . . . 23
4-2. ANALOG AMPLIFIER ClRC",TRY : : : : : : 23
4-3. ANALOG-TO-DIGITAL CONVERTER. . . 26
4-4. POWER SUPPLY . . . .
4-S. MODEL 16028 DIGITAL OVTPUT . : : ,'P
5. ACCESSORIES. . 32
MODEL 1601 AC DC PROBE 32
MODEL 1688A RECHARGEABLE BATTERY bAiK: : . .
MODEL 1683 UNIVERSAL TEST LEA0 KIT ., . .
::
MODEL 1600 HIGH VOLTAGE PROBE.
MODEL 1682 RF PROBE... . ::
MODEL 1609 CALlBRATlON COVER . .
34
MODEL 1681 CLIP-ON TEST LEAD SET
6.. "AINTENANCE. .
2
6-1. GENERAL.
6-2. REQUIRED TEST EQUIPHENT. t ::
6-3. PERFORMANCE VERIFICATION . . 35
b-4. ADJUSTMENT/CALIBRATION PROCEDURE 37
7. REPLACEABLE PARTS. ........... 45
7-l. GENERAL. ............. 45
7-2. ORDERING INFORMATION ....... 15
7-3. SCHEMATlCS 45
ii
ILLUSTRATIONS
rzg. NO. IIcLe rage
1 "fme"sio"al Data. --___--____-____-_____________________ iv
2 Tilt Bail Positions. ------------------------ vi
3 *pant panel. ------------------------------------------- 1
4 *ottcm View Showing Line Cord. -------------------------
5 Rear View Showing Line Switches. -------__--_____--_____ 3
6 Mode11688A Rechargeable Batrery Pack. ------------------ 4
7 Exploded View of Model 160B/1688A.---------------------- 4
8 Installatio" of Battery Pack. ------------------------
9 Battery Test Location. ------------_----___------------- ;
10 Front Panel Controls. -------------------_-------------- 9
11 Imcarion of Protection Fuse. _---____-_________-________ 11
12 Voleage Measurements "sing Model 1601 AC/DC Probe. ----- 13
13 Current Measurements Using Made1 1651 Shunt. ---------- 13
14 Floating operation. --_---__-__-_______________________ 14
15 Model 16028 ,,+&tal O"f,,"t. _____-____-___-____-________ 15
16 Exploded View of Model 16011602B. __-_-----__--____--__ 16
17 lnstallati,,,, of &,&I 1602~. _---_______-____-__________ 17
1.8 Rear Panel Digital output Connector. ------------------- 18
19 Timing Diagram for Model 1602~. ------------------------ *"
20 Rack M,,unti,,g of Model 1.3,~. __--_______--______________ 22
21 Overall Block Diagram. _---____-___-____--_____________ 23
22 DC Voltage Operation. -------------_----__------------- 25
23 Resistance operation. __-____-_________--______________ 25
24 current Operaelan. ------------------------------------- 25
25 Absolute Value Deeector. ---__--_-________-_____________ 27
26 LSI Block Diagram. ----_---___----___--_________________ 28
27 A/D Converter Diagram. _--___-_________--_______________ 28
28 Identification af Se~,ent.s and Mulriplex lines. -------- 29
29 Tap and Bottom Cover Assembly. ------------------------- 38
30 Locarion of Calibration Ad,ustmenfs. ------------------ 40
31 Location of Test mints. 41
32 Location of Chassis Connections. ---------------------- 44
33 Location of Fuses. ------------------------------------- 44
34 case Outline - Integrated CirCUitS. -------------------- 54
35 case Outline - Integrated circuits. _---_______________- 55
36 Case Outline - Integraeed Circuits. _--____--_____--__- 56
37 case Outline - Inregrated circuits. -------------------- 57
38 case ourline - Transistors. 58
39 Case Outline - Thick Film Networks. _---__-_____-_______ 59
40 Case Outline - Thick Film Networks. -------------------- 60
41 Case O"tline - Custom LSI. ---_----_---_-_------------- 61
42 Component Layout* pc-349. --_-_--______________________ 63
43 component Layout, pc-352. ----_---_-----____--_______I_ 64
0976
SPECIFICATIONS MODEL 1608
I
10.7 5
(27:
i
I
DIMENSIONS IN INCHES (MM)
I
FIGURE Dimensional
1. Data.
1174
SPECIFICATIONS
Calibrated at 25" *ST
war,mte* to, 1 year
AS A DC VOLTMETER
AS AN OHMMETER
Liz2
NORMAL BENCH POSITION
m
LEVEL POSITION - TILTEAIL AT FRONT
J
& 45" POSITION
-
LEVEL POSITION - TILTBAIL%
MODEL 160B
SECTION 1. GENERAL INFORMATION
l-l. INTROD"CTION. The Model 1608 is a wide-range
digital multimeter capable of measuring voltage, cur-
rent, and resistance. me Model 1608 offers SeYen
ranges of voltage from lrn" to 1000 volts, nine ranges
of current from 1O"A to 1ooomA, and ten ranges Of re-
sistance from 1n to lOOOM12. The Model 1608 display
is 3 digifs plus 100% overrange.
1-2. FEATURES.
a. Voltage sensitivity to 1 micravole per digit.
b. current .se"Giti"ity to O.OlnA per digit.
C. Resistance sensitivity to 0.001n per digit.
d. Floating capabilify LO _+1*00 "OlC.5 above case.
e. Built-in analog output.
f. Optional Made1 1602R Digital Output
s. Optional Model1688ARrchargeable "attery Pack.
HANDLE AND
TILT BAIL
I
LINE
COW
STORAGE
~
S S
BAT TEST A
BAT TEST B
I
CONDENSEDOPERATING INSTRUCTIONS S = SCREW
LOOSEN FOR
DISASSEMBLY
2 1174
MODEL 1608 INITIAL PREPARATION
5112 J113 !520 I DiGi :TAL
ANALOG OUTPUT OUTF 'UT
J302
SWITCHES SHOWNFOR
OPERATION FROM 105-125V LINE
3
L`IG"RE 7. Exploded view Of Model 1600,16881\
4 0976
I BATTERi FUSES
I F203, F204
I
MODEL 1608 CHASSIS \\
SPACER
(4 PLACES)
CAUTION
DISCONNECT LINE CORD BEFORE OPENING
THE TOP AND BOTTDM COVER,
LINE VOLTAGE ON THE CHASSIS
REPRESENTS A SHOCK HAZARD.
I
FIGURE
8. Installation "f Battery Pack.
0976 5
INITIAL PREPARATION MODEL 160B
SECTION 2. INITIAL PREPARATION
2-l. GENERAL. This section provides information b. Row to operate From Battery Power. TO operate
needed for incoming inspecrian and preparation for the Model 16OB from batteries, the Model 1688A Re-
use. chargeable battery Pack must be installed. The Model
1688A can be either field or factory installed. (The
2-2. INSPECTION. The Model 1603 was carefully in- batteries in the Model 1688A may need recharging be-
spected both mechanically and electrically before fare their first usage to power the Model 1600.)
shipment. "pm receiving the instrument, check for
any obvious damage which may have occurred during NOTE
f*El"Sit. Report any damages to tne shipping agent.
TO verify the electrical specifications, follow the The Model 1688A Rechargeable Battery Pack can
procedures given in Section 6. be insralled within the Model 1608 chassis at
any time. However, if the Model 16028 Digital
2-3. PREPAR**ION FOR "SE. The Model 160~ is shipped Output is already installed, the Model 1688A
ready-to-use. The instrument can be powered from cannot be used simultaneously.
line voltage or from rechargeable nickel-cadmium bat-
teries (when the oprional Model 1688A Rechargeable 1. HOW to Install Model 168% Rechargeable Bat-
Battery Pack is installed). tery Pack. The batteries furnished with the Model
1688A come already installed in the battery pack.
a. How to operate From IdlIe Power. The Model 16OB the battery pack includes 7 rechargeable "C" cells
provides a three-wire cord which mates with third-wire (1.2", 3 AMP HR) and 1 rechargeable pack (16.8V).
;rounded receptacles (see Figure 4 for ~1% configura-- If baeeeries need to be replaced or re-installed,
tion,. the permanently installed line cord is stored be certain to observe the proper polarity of indi-
by wrapping the card around the base of the i"str"- vidual cells as shown in Figure 6. To install the
ment as shown in Figure 4. Model 1688A Battery Pack, turn the instrument over
so that the bottom cover faces up. Loosen four
1. wow to Set Line Switches. The Made1 1608 has slotted screws on the batrom cover as shown in
two rear panel Line Switches which enable selection Figure 4. (A chisel-blade screwdriver is requires'
of line voltages over ranges from x0-llO", 105125v, to loosen the slotted screws.) Turn over the in-
195-235", or 210-250". TO operate from line power. strument with tap cover facing up, taking care to
determine the appropriate line voltage range to be hold the top and bottom covers together. Carefully
used and set the Line Swirches as fallows: remove the top cover to gain access fo the printed
circuit board. (Two "ires that connect to the
TABLE 2-1. Analog Oufput must be disconnected at the PC board
Summary of Line Switch Settings. before the top cover can be set aside.) Check to
I see that the four insulating spacers are in yasi-
tion on the printed circuit board. Place the Model
1688A Battery Pack in position an the spacers with
I
NORM,
105-125" 117
`Jo-110"
195-235"
I LOW. 117 I the cable oriented as sham in Figure 8. Plug the
4-wire Conneceor (5205) into the mating receptacle
I 1
210-250"
LO", 234
NORM. 234
(P205) taking care to orient
shown in Figure 8. After
stalled. replace
the connector
the Battery
the top cover.
as
Pack is in-
Turn over the in-
For example, if the line voltage ea be used is strumen; wiih bottom co&r facing up and tighten
approximately 115 volts, select NORM and 117 which down the four slotted-head screws.
permits B range of operarion from 105 to 125v.
hfter line Switches are set, connect the line cord TABLE 2-2.
and set the Power Switch to LINE. Sumnary of nateerie Used in Model 1688A
2. ,.ine Fuse Requirements. The Model 1608 uses
~VO line fuses to protect the line-operated power
SWPlY. ne fuse types are l/8 ampere, MB, slow-
blow. Replace with Keithley Part No. F"-20. Rechargeable "C" cell,
1.2". 2 AMP-FIR
Rechargeable battery 1 TM-32
3. How to Replace Fuses in Model 1688A. The pack, 16.8V, .225
!Jodel, 1688H uses 1 ampere fuses to protect the Am-m
power supply regulators in case of malfunction.
Fuses F203 and F204 are plug-in types and are lo-
cated on pc board PC-349 as shown in Figure 8.
Keplace with 1 ampere, 3AB, slo-blo, Keithley Part
NO. FU-28.
6 0976
The instrument must he operated in the BAT
mode in order t" obtain a valid battery con-
dition at test points A and 8. This3 Will
enstire that tile batteries are supplying
power to the instrument. If the voltages
are measured when the Model 1608 is opera-
ted in the LINE mode a different reading
may be observed since the batteries are not
connected and rherefore do not supply power
to the instrumenr.
0976
OPERATING INSTR"CTIONS MODEL 160B
SECTION 3. OPERATING INSTRUCTIONS
3-l. GENERAL. This sec~ian provides information 3-3. HOWTO MAKE INPUT CONNECTIONS. The Model 1608
needed to operate the Model 160B for measU*eme"f Of has two front panel terminals identified as "HI"
voltage, cuirent, and resistance. (red) and '3.0" (black). These terminals accomodate
banana plugs. alligator clips, spade lugs, bare
3-2. HOW TO SELECT POWER. The Model 160B may be wirea, and other similar input connections. Leads
powered from line voltage or rechargeable nickel-cad- may be fabricated using a good quality capper wire
mium batteries ("hen the Model 1688A is installed). terminated by single banana plugs such as Keichley
The Model XOB has a built-in line-voltage power sup- Part No. K-5 or dual banana plug such as Keithley
ply and line cord. If the accessory Model 1604 Re- Part NO. m-7. Ready-made test leads are also avail-
chargeable Battery Set is ordered and installed, then able from Keithley. Accessory Model 1681 Clip-o"
the user has the oprion of selecting line or bateery Test Lead Set includes two 40 inch long leads ter-
operation via the front panel rotary power switch. minated by a banana plug and spring-loaded clip which
easily attaches co wires and terminals on pc boards,
NOTE etc. Model 1683 Universal Test Lead Kit features in-
terchangeable probe tips for various applications.
The accessory Model 1688A Rechargeable Bat- 'I%e Kit includes regular probes, alligator clips,
tery See may be ordered at ebe time of pur- banana plugs. spade lugs, and phone tips. All-cow==
chase of the Model 160B or may be purchased leads and teminarions are best for measurements on
and field installed at a later time if so the lm" and ln ranges.
desired. me Model 1688A features plug-in
Wi*i"g. As a result, no modifications need
to be made to the Model 160B chassis.
a. "m, to Operate from Line Power. The Model 160B
can be powered from Line voltage over four ranges
from a minimum of 90" to a maximum of 25OV. see 3-4. HO" TO SELECT FUNCTION. Function is selected
Table 2-1. by means of a single front panel Range Switch. llie
Range dial is marked in "en&wring" units for meas-
1. Set rear panel Line Switches to appropriate "remenf Of voltage (rn", V), C"r*e"t ("`4, LL4, n!A), and
positions as show" in Figure 5. resistance (`2, kn, M0). For each function, rotating
the knob clockwise causes the Model 160B to switch
to a less sensitive range.
3. Set front panel Power Switch to LINE. a. DC "catage. The voltage sectors of the Range
Switch are designated in millivolts ("IV) and volts
b. "cm to Operate from Battery Power. I", for full ranees from lm" to 1000". A full stop
it'the 1000 "&range prevents inadverranr switch-
I. Install Mode11688ARechargeable Battery Pack. ing to the nanoampere ranges by clockwise rotation.
2. Check battery voltages at Teat Points A and b, Resistance. The resistance sectors of the
B to ensure thaL batteries are charged sufficiently. Lange Switch are designared in ohms (n), kilohms
(kn), and megohms (MO) for full ranges from 1 ohm
1. If necessary, plug line cord info ac power to 1000 megohms.
and set Power Switch to CHG to bring battery "alt-
age up to useable levels. C. CU**e"t. The current sectors of the Range
Switch are designafed in nanoamperes ("A), micro-
4. When bartery level is sufficient, disconnect amperes (,,A), and milliamperes (mA) for full ranges
line cord and set Power Swifch LO BAT. franI 10 nanoamperes to 1000 milliamperes.
Condition of Instrument
switch Line Connected Line connected Line not connected
POSition 1688A not installed 16888 installed 1688~ installed
OFF OFF OFF
LINE ON ON
CHG OFF ON
BAT OFF ON
8 0976
-ZERO
R114
POWER
S203
- RANGE
SlOl
FIGURE 10. Front Panel Controls.
3-5. HO" TO ME`"LS"RE"OLTIICE. The Model 1608 meas- b. How to Determine Accuracy. The xodel 16011 nc-
ures dc "aleage in seven ranges: Im", lOnl", loom", curacy is iO.I% of readina f 1 dirit. For enarno1e.
lV, lOV, LOO", and 1ooov. Maximum dc input is 1200" a display reading of 1.005 volt dc will have a" ,a,,-
dc + peak ac. certainty of 10.1% f 1 digit or r.002 volts. The in-
put resisrance in the dc m"de is 10 o,c~",,cs. !,eai-
a. How to Select Ra"E,e. Function and range is urements from relatively high source resistnnccs
selected by rotating the Range Switch to the appro- could cause an additional reading error. The dln"",:i
priate position. Three positions are direct-reading of error due to loading can bc determined by rhc
in millivolts CmV); four positions are direct-read- following relatiansbip:
ing in voles (VI. Decimal point is selected by the
Kan,qe Switch. Polarity is automatically displayed. % error = 100 x RS i (R, + 10')
If the input signal exceeds twice full range, the where R, = Source resistance in ohms
display blanks (3 least significant digits) to in-
dicate an "overran& condition. For example, a so"rcc resistance "f 10,000 ohms Viii
result in a loading error of approximately 0.1% ai
TABLE 3-2. reading.
"01 1tage Ranges Displ; d
Range
SeCti" Max. Display The input current of the 1608 Cal" also cause
reading errors on the nlOSL sensitive vo1cage
1000 v 1999 * ranges when high source resistances are pre-
100 v 199.9 sent. For example, an input CUrrent of lOpA
10 v 19.99 and a so"rce resistvnce of MI! produce a"
1 v 1.999 error voltage of loll".
, 100 mv 199.9
10 mv 19.99 c. Maximum Allowable Input. The maximum L"P"L to
1 In" 1.999 the Model 1608 is 1200" dc + peak ac. On lrn", lOn,V,
and lOOn," ranges, the maximum conti"uox,s input is
*Maximum allowable input is 1200" dc plus 6OOV (12OOV momentary) dc + peak ac. `,`hc ?,odel ,,SO"
peak ac even though display can be read can display dc voltages greater tba" r120O" but dnm-
beyond 1.200". age to the input is possible.
1174 0
OPERATING INSTR"CTIONS MODEL L6OB
IMPORTANT 1-6. HOWTO MEASURE RESISTANCE. The Model 1608
measures resistance in 10 ranges: lsr, 1on, 10011,
The Model 1608 provides ac rejection (NMRR) Ikn, IOk&?, lOOk0, IM,,, lOMn, lOOK,, and 100011!2.
of greater than 60 dB on the highesf range.
However, a large ac signal superimposed on a. HO" to Select Range. Function and range is
a dc level could cause damage if the input selected by rotafinf: the Ranae Swifch LO rhe BPPTO-
CO the Model 160" exceeds 1200 volts dc + priate position. Three posi;ions are direct-reading
peak UC. in ohms (n): three positions are direct-reading in
kilohms (kn); four positions are direct-reading in
d. How to Zero the Display. To accurately zero megohms (MQ) Decimal point is selected by Range
the instrument, place a low-thermal short (such as a Switch. If the input signal exceeds twice full range,
piece Of clean copper wire) across the input rermin- the display blanks to indicate an "overra"& condl-
als, set Lhe Range Switch to the lm" range, and ad- ti**.
just the front panel Zero conerol for a flashing "i"
sign at the display. The display should then read TABLE 3-3.
t.OOO, with some flicker of the least significant Resistance current Ranges
digit due to noise and A-D converter uncertainfy.
Range Max. Impressed
Once the zero has been set accurately, there should setting LIiF3play units current
be little reason to rezero the instrumenf again soon
when making measurements on the 10~1" through 1000" 1. n 1.999 ii I InA
ranges. The time stability of rhe zero setring is 10 n 19.99 n lti
excellent, and in applications requiring continuous
operation of the Model 160B, the zero setting will
hold for months. The front panel Zero control is
convenienf when making measurements on fhe 11"" Range.
1 MI1 1.999 Mn 100 "A
A test set-up and cables when connected to the 160B 10 Mn 19.99 MO 10 "A
may cause offset voltages because of thermoelectric 100 Mr! 199.9 Mn I"`4
effects (see section 3-9). These offset voltages 1000 M* 1999 MO 0.1 "A
might be only a few microvolts or several tens of
microvolts. In such situations, the Zero control b. How to Determine Accuracy. The accuracy of cbe
can be used to buck out any initial offsefs. I."" Model 1608 is specified in terms of a nercen~ of
thermal cabling and connections should be used when- reading and a p¢ of range. For example, a dis-
ever possible. The instrument zero can also be check play of 1.000 kilohID (kn.1 will haw an uncertainty
ed, and adjusted, by shorring the input on any range of ~0.004kQ.
(voltage, current, or resistance). me zero c**t*01
will have varying effects on the differenr ranges C. HO" to Measure "LOW" ohms. when making meas-
depending on the sensitivity of the input amplifier, urements on the ln, lOn, and 1OOn ranges, rhe Model
but the zero control can be used in this manner. 160B is to be zeroed on the IQ range. The zeroing
Again, it should be emphasized, that for most meas- is accomplished by shorting the test leads together.
"remene~ with the Model 160B, the Zero control can and adjusting the display for a flashing + and -
be set once and then left untouched. (See also ?ec- .ooon. By zeroing the instrument in this manner,
tion 3-6c "LO" Ohms Zeroing"). lead resistance of 200 mill.iohms (minimum) can be
compensated for. The instrument must be rezeroed on
NOTE the lil range each time a different set of iese leads
is used. Before making meaS"reme"tS right *t the in-
With the input open 0" the lm" Range, the put rerminals (no test leads used), rhe instrumene
Model 160~3 display may show a reading as should be zeroed on the iii Range after placing a
high as i.100. This 19 equ*va1ent to an short, such as a piece of copper wire, across the
offset currene of lo.opA. If the display binding posts. Copper leads and clips are best for
shows a reading grearer than t.100, then making measurements on the ln Range, because the
the internal potentiometer, R121, should voltage drop across a In resistor is only Im".
be readjusted. Typically, ehe offset cur-
rent will be less than 5p~. CAUTION
e. 80" to "se Model 1601 AC/DC Probe. Care should be taken when making resistance
TO make ac measurements in circuits which may have volt-
measuremenfs, connect the Model 1601 accessory K/DC
Probe to the Model 1608 inpur terminals. ages on capacitors, etc. or "here line volt-
Set the age is present. Although the Model 1608 is
Range to desired voltage range. Set switch on probe
to AC. "se the probe tip plus ground clip to make fully protected against accidental voltages
connections to circuit under eesc. up to 250" rms in resistance function, if
see section 5 for
complete specifications. higher voltages are applied, damage may occur.
f. How to "se Model 1682 RF Probe. To make rf ac
measurements, connect the Model 1682 Probe to the
Model 160B input terminals. Set the Range to desired
voltage range. Maximum allowable input is 30" *Ins
ac, 200" dc.
10 1174
-FUSEFUSE SHOWN
TWICE ACTUAL SI
Range Max.
setting IDisplay Units s,,une R*
I,0 nA 19.99 Il.4 1060
100 nA 199.9 IL4 10%
1 LB.4 1.999 II`4 1040
LO ,lh 19.99 irA 10311
100 UA 199.9 UA 10%
1. InA 1.999 n!A 10 il
10 rnA 19.99 In.4 I. 0
100 lx.4 199.9 mA 0.1 !1
1000 mi\ 1.999 ti 0.1 G
OPERATING INSTR"CTIONS MODEL 160B
d. HOW to "se the Model 1651 Current Shunt (for 3-11. AC ELECTRIC FIELDS. The presence of electric
meaS"remenfS to SOA). current measuremenf capability fields generated by power lines or other sources can
Of the Model 160B may be extended to 50 amperes have an effect on instrument operation. AC voltages
through ctle use Of accessory Model 1651 SO-Ampere which are very large with respect to the full-range
shunt. The Model 1651 permits 4-terminal connections sensitivity could drive the input amplifier into sat-
to minimize meaeuremene error.ciue to lead resistance. urarion, thus producing an errOneo"S DC OUtpUt. At
To use the Model 1651, connect the voltage sensing line frequency or twice line frequency, the insLru-
leads eo the Model 160B input terminals. Connect ment is capable of rejecting AC voltages whose peak-
separate current leads (not furnished) beuveen xhe to-peak amplitude is equal to the full-range DC sell-
source and the large hex-head bolts on the Model 1651. sftivity on the loom" through 1OOOV ranges. This
The current leads should be rated for currents up to level of interfering AC signal will produce no more
50 amperes. me Shunt resistance is 0.001 ohm, vhich than 1 digit error. On the lm" and 1OmV Ranges, the
produces a sensitivity of lmV/Amp. As examples, 10 instrumenf can reject line frequency and twice line
amps current results in a lOIn" drop on 1Oln" RANGE, frequency signals whose p-p amplitude is equal CD 10
and 30 amps yields a voltage drop Of 3Oln" which can eimes the full-range sensitivity. Far example, on
be read on the loom" RANGE. Power diss*paCed in the rhe ID," Range, a 1OmV p-p, 50 Hz signal will produce
shunt is 2.5 watts at 50 amperes. no more than 1~" (1 digit) DC erroi-. Peak-to-peak AC
voltages greater than 1x the full-range sensitivity
o,, the 1OOm" through 1000" ranges, the 10X the full-
3-8. NOISE CONSIDERATIONS. The 1imic of resolution range sensitivity on the lln" and 1omv ranges will
in voltage and current measurements is determined cause clipping in the AC section of the Model 160B
largely by rhe noise generated in the source. stray input amplifier. For this reason, shielding is re-
low-level noise is present in some form in nearly al1 com,,,ended when making sensieive DC voltage measure-
electrical circuits. The instrument does not distin- menrs, or when making measurements from high so"rce
guish between stray and signal voltages since it meas- impedances. (See Shielding, Section 3-12.) The in-
ures the net "olfage. when using the lnl" and 1omv serunlent is also capable of rejecting frequencies
ranges, consider the presence of low-level e1ectri- other than power line frequencies. There is one pro-
cal phenomena such as thermocouples (thermoelectric blem to consider; however, the input amplifier of the
effect), flexing of coaxial cables (triboelectric Model l6OB uses a modulator to convert DC signals LO
effect), apparent residual charges on capacitors AC signals before amplification. The drive frequency
(dielectric absorption), and battery action Of t"O of this modulator is 220 HZ nominally, f approx. 5%.
terminals (galvanic action). Interfering AC signals with frequencies equal to the
modulator drive frequency, or mu1tipl.e~ fhereof, will
appear 8.3 modulated DC, and produce large DC errors.
3-9. THERMAL EMFS. Thermal emfs (thermoelectric 3-12. SHIELDING.
potentials) are generated by thermal differences be-
tween two junctions of dissimilar metals. To mini- a. Electric Fields. Shielding is usually necea-
mize the drift caused by thermal emfs, "se copper 8arv when the insrrument is in the eresence of verv
leads to connect the circuie to the instrument. The l&e a-c fields or when very sensi;ive measuremen;s
front panel ZERO control can be used to buck out a are being made. The shields of rhe measurement cir-
cmstant thermal offset "aleage if necessary. The cuit and leads should be connecee* together to ground
Keithley accessory Model 1483 La" Thermal. Connecrio" at only one point. This provides a "tree" configura-
Kit contains all necessary materials for making very tion, which minimizes ground loops.
low thermal copper crimp connections far minimizing
thermal effects.
b. Magnetic Fields. Magnetic shielding 19 useful
where very large magnetic fields are present. Shield-
ing, which is available in ehe form of plates, foil
or cables, can be used to shield the measuring cir-
cuit, the lead wires, or the instrument itself.
C. Other Considerations.
3-10. MAGNETIC FIELDS. The presence of strong mag-
netic fields can be a potential sw.,rce of ac noise. 1. Voltmeter Measurements. Use shielded input
Magnetic flux lines which CUt a conductor can produce leads when source resiseances are greater than 1
large a-c noise especially at power line frequencies. kilohm or when long input cables are used.
The voltage induced due to magnetic flux is propor-
tional fO the area enclosed by the circuit as well 2. Current Measurements. On the mA and PA cur-
as the rate of change of magnetic flux. For example, rent ranges, no special shielding precautions need
the motion of a 3-inch diameter loop in the earth's be taken. However, an the 100 and 10 nanoampcre
magnetic field Will induce a signal of several tenths ranges, shielded input leads are recommended.
of a microvolt. one way to minimize magnetic pickup
is to arrange all wiring so that rhe loop area en- 3. llesiatance Measurements. Shielding of input
closed is as small as possible (such as twisting in- leads and source are recommended for measurements
pur leads). A second way co minimize magnetic pickup on the 10 megohm through 1000 megohm ranges to pre-
is to use shielding as described in Section 3-12. vent errOneO"S readings.
12 1174
FIGURE 12. Voltage Measurements Using Model 1601 AC/DC Probe.
CURRENT TERMINALS
VOLTAGE TERMINALS
VOLTAGE LEADS FURNISHED
;*
1
1174
OPERATING lNSTR"CTlONS MODEL 1608
I MODEL 1608
--~
i+ EXTERNAL
E%' TYPICAL
DC >lO"n ISOLATION
I
RESISTANCE
CASE 8'
GROUND
FIGURE 14. Floating Operation
3-13. HOWTO USE THE ANALOC OUTPUT. The Model 16OB
has an analog output of il volt at full-range (non-
inverting) at up to 1 milliampere (2mA at 2 volts)
for recording or monitoring purposes. Also, the
analog output enables the Model 1608 to be used as
a la"-noise, low drift DC amplifier.
TABLE 3-5.
hi" at liNALOG OUTPUT
Full Range "across lk = I x lkn = 10-a x 103 = lOll"DC
Range Gain OUtpUt The "isolation" capacitance from LO to GNC is impor-
tant when AC common-mode signals are present. in
1 In" x1000 1" the Model 1608, rhis capacitance is specified at 300
1.0 rn" x100 1" pF maximum. At a frequency of 60 HZ, 300 picofarads
100 In" x10 1" has a reactance of approximately 10Mli. With the HI
terminal driven and a source impedance of lkll, R
For off-ground operarim, the analog output should 1OOOV p-p, 60 Hz, common-mode signal will produce a
be connected only to equipment capable of operating voltage of only loom" p-p across the Model 1608 in-
off-ground also. The low side of the analog output put terminals. This lOOmV p-p signal will be lurtbcr
is at the same poeential as the "LO" input terminal rejected by the input amplifier and A-1) converrer SC
of the Model 160". that the total rejection at the digital display is
at 1easL 140 LIB. At lower levels of *C common-mode
3-14. HOW TO USE MODEL 1608 OFF-GROUND. The "LO" signals, the total rejection at the display is even
terminal can be operated off ground at potentials greater. For example, a 60 Hz, 100" p-p signal
Of up tLl 11200". Isolation franI ehe "LO" terminal should produce only about 1 digit errur on the lh"
to power line ground is specified at lOOOMn, or 10'0 Range for a total rejection of approx. 160 dR. (IiT
(shunted by 300@). Ty,,ically, the isolation resis- driven, IkQ source impedance.1 WiCh both AC and IDC
tance from I.0 to GNE is two decades greater than common-mode signals, rejecti,, is lnuch greater than
log!? (lO"O). Because of this excellent isolation, specified when the Model 160B LO terminal is driven,
operating the Model 1608 off ground results in very rather than the HI rerminal. Where there is a need
1.itr1e loading (from LO to GNU) of a floating source. for even greater isolation from LO (0 power Line
AC 1000" above ground, the Model 1608 will require, ground, or where there is a need fo float at porcn-
typically, only 1Onh from the source. The excellent tials greater than UOO volts above power Line ground
i.solation also accounts for the high common-mode re- the Model 1688A Battery Pack should bc used.
14
MODEL 160B OPERATINC INSTRUCTIONS
out&t IO& "0" s &Sure f0 0~tp~f LO.
OUtput Device: 2N5089 or equivalent (greater than
25volt breakdown, less than 0.5 volt while sink-
ing f15 milliamperes).
REMOTE CONTROLS:
Strobe: 6 lines for serializing in multiples Of 4
i' bits. Logic "1" inhibits controlled OUtpUt lines.
O"t"UC Hold: I.oeic "0" retains data from last read-
ing af DigitLOutput.
Display Hold: Logic "0" retains data from last
reading (escept far polarity and decimal) at
"igital output and Display.
0976 15
CwmATING INSTR"CTIONS MODEL 160B
FIGURE 16. Exploded View of Model 1608/1602B
3-15. HOW TO USE MODEL 16028 DIGITAL OUTPUT. To install the Model 16028. turn the Model 160B "ver
.
so mar: me DOttOm cover races up. Locate and loose"
a. General. The Model 16028 Digital Output provides four slotred scre"s as shown in Figure 4. The 8cre"B
binary-coded decimal (BCD) ouepufs and several control are "captive" and should "at be completely removed.
inputs. 2his accessory is available either "fsctary- Once the screws are loosened, hold top and bott"m
installed" or "field-i"srallable". The Model 1602B covers ragether and turn Wodel 1608 so chat the top
consists of a single printed circuit baard (K-352) CO"Br- is up. Carefully lift off rhe top c"ver and
with input and integrally mounted "u~pue ca""ecfar, disconnect the wires to the Analog Output. Locate 16-
and an ouf,,"t mating cm,ne~tc,r with hoad. pin receptacle 5201 o" the ma,." circuit board W-349).
Plug the mating c""necLor (P301) from the Model 1602B
b. Installation of Model 1602B. The Model 16028 into 5201, after checking that pin numbers are corres-
ia installed inrernal to the Model 160B and is DOW~I- ponding. Locate Spin plug P208 on the main circuit
ed by the Model 1608 line operated power supply: b"ard (PC-349). Connect 5303 from the Model 1602B to
P208. Be sure that the "A" of PZOE lines up with the
NOTE "A" af 5303. Place Model 1602B board o" four spacers
with cables positioned as shown in Figure 17. Rem"ve
It is not ineended that the Model 16028 be digital-output c"v◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo