Keithley 1602B, 160B Service manual
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
FOURTH PRINTING, DECEMBER
1975,
KEITHLEY INSTRUMENTS, INC.
1977,
CLEVELAND, OHIO, U.S.A.
CONTENTS
:,OOEL ibOJ
CONTENTS
-
SECTION
SPECIFICATIONS. .
I. GENERAL INFORMATION.
I-l, ,NTROD"CT,ON
......
........
. .
i-2. FEATURES
l-3. WARRANTY lNFORHATlON.
l-4. CHANGE NOTlCE
................
............
l-5. OPTIONAL MODEL 16028 D,G,TAL o"TP" T.
1-6. OPTIONAL MODEL 1688~ RECHARGEABLE BATTERY PACK
2. INITIAL PREPARATlON
................
2-l. GENERAL ...................
2-2. INSPECTlON.
Z-1.
PREPARATION FOR "SE
.................
3. OPERATlNG INSTRUCTIONS . .
3-l. GENERAL
3-2. HOW TO SELECT POWER. .
3-3. HOW TO MAKE INPUT CONNECTION!
3-4. HOW TO SELECT FUNCTlON
HOW TO MEASURE VOLTAGE
3-5.
3-b.
HOW TO MEASURE RESISTANCE.
3-7. HOW TO MEASURE CURRENT .
3-8. NOISE CONSIOERATIONS
.
3-9. THER"AL EHFS . .
3-10. MAGNETIC FlELDS .
3-11. AC ELECTRlC FIELDS .
.
*
3-12. SHIELDING. .
3-13. HOW TO "SE THE ANALOG OUTPUT
3-14. HOW TO USE MODEL 1608 OFF-GROUND . .
3-15. HOW TO USE MODEL
16028
DlGlTAL OUTPUT.
3-16. HOW TO RACK MOUNT THE MODEL 1608
4
THEORY OF OPERATION. . . . . . . . . : :
4-l.
GENERAL .
4-2.
ANALOG AMPLIFIER ClRC",TRY : : : : : :
4-3. ANALOG-TO-DIGITAL CONVERTER. .
4-4.
POWER SUPPLY . . . .
4-S.
MODEL 16028 DIGITAL OVTPUT . : :
ACCESSORIES. .
5.
MODEL 1601 AC DC PROBE
MODEL 1688A RECHARGEABLE BATTERY bAiK: :
MODEL 1683 UNIVERSAL TEST LEA0 KIT
MODEL 1600 HIGH VOLTAGE PROBE.
MODEL 1682 RF PROBE... .
MODEL 1609 CALlBRATlON COVER .
MODEL 1681 CLIP-ON TEST LEAD SET
6.. "AINTENANCE.
6-1. GENERAL.
6-2. REQUIRED TEST EQUIPHENT. t
6-3. PERFORMANCE VERIFICATION .
b-4.
7. REPLACEABLE PARTS.
ADJUSTMENT/CALIBRATION PROCEDURE
...........
7-l. GENERAL. .............
7-2. ORDERING INFORMATION
.......
7-3. SCHEMATlCS
.....
.
I
. .
.
.
PAGE
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32
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35
37
45
45
15
45
ii
ILLUSTRATIONS
rzg. NO.
1
2 Tilt Bail Positions. ------------------------
3 *pant panel. -------------------------------------------
“fme”sio”al Data. --___--____-____-_____________________
4 *ottcm View Showing Line Cord. -------------------------
5
Rear View Showing Line Switches.
6 Mode11688A Rechargeable Pack. ------------------
IIcLe
-------__--_____--_____
Batrery
7 Exploded View of Model 160B/1688A.---------------------8 Installatio" of Pack. -----------------------9
Battery Test Location.
Battery
------------_----___------------10 Front Panel Controls. -------------------_-------------11 Imcarion of Protection Fuse. _---____-_________-________
12 Voleage Measurements "sing Model 1601 AC/DC Probe. -----
13 Current Measurements Using Made1 1651 Shunt. ---------14 Floating operation. --_---__-__-_______________________
15 Model
16
16028
,,+&tal O”f,,“t. _____-____-___-____-________
Exploded View of Model 16011602B.
__-_-----__--____--__
17 lnstallati,,,, of &,&I 1602~. _---_______-____-__________
1.8 Rear Panel Digital Connector. -------------------
output
19 Timing Diagram for Model 1602~. -----------------------20
Rack M,,unti,,g of Model
1.3,~.
__--_______--______________
21 Overall Block Diagram. _---____-___-____--_____________
22 DC Voltage Operation. -------------_----__------------23 Resistance operation. __-____-_________--______________
24 current Operaelan. ------------------------------------25 Absolute Value Deeector. ---__--_-________-_____________
26 LSI Block Diagram. ----_---___----___--_________________
27 A/D Converter Diagram. _--___-_________--_______________
28 Identification af Se~,ent.s and Mulriplex lines. -------29 Tap and Bottom Cover Assembly. ------------------------30 Locarion of Calibration Ad,ustmenfs. -----------------31 Location of Test mints.
32 Location of Chassis Connections. ---------------------33 Location of Fuses. ------------------------------------34 case Outline - Integrated CirCUitS. -------------------35 case Outline - Integrated circuits. _---_______________36 Case Outline - Integraeed Circuits. _--____--_____--__37 case Outline - Inregrated circuits. -------------------38 case ourline - Transistors.
39 Case Outline - Thick Film Networks. _---__-_____-_______
40 Case Outline - Thick Film Networks. -------------------41 Case O"tline - Custom LSI. ---_----_---_-_------------42 Component Layout* pc-349. --_-_--______________________
43 component Layout,
pc-352.
----_---_-----____--_______I_
rage
iv
vi
1
3
4
4
;
9
11
13
13
14
15
16
17
18
*"
22
23
25
25
25
27
28
28
29
38
40
41
44
44
54
55
56
57
58
59
60
61
63
64
0976
SPECIFICATIONS
I
10.7
5
(27:
MODEL 1608
i
DIMENSIONS IN INCHES (MM)
I
FIGURE 1.
I
Dimensional Data.
1174
SPECIFICATIONS
Calibrated at 25” *ST
war,mte* to, 1 year
AS A DC VOLTMETER
AS AN OHMMETER
Liz2 m
NORMAL BENCH POSITION
LEVEL POSITION - TILTEAIL AT FRONT
J
&
45" POSITION
-
LEVEL POSITION - TILTBAIL%
MODEL 160B
SECTION 1.
l-l. INTROD”CTION.
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 resistance 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.
current .se"Giti"ity to O.OlnA per digit.
b.
Resistance sensitivity to 0.001n per digit.
C.
Floating capabilify LO _+1*00 "OlC.5 above case.
d.
e. Built-in analog output.
Optional Made1 1602R Digital Output
f.
Optional Model1688ARrchargeable "attery Pack.
s.
The Model 1608 is a wide-range
GENERAL INFORMATION
HANDLE AND
TILT BAIL
I
BAT TEST A
BAT TEST B
S
~
I
CONDENSED OPERATING INSTRUCTIONS
LINE
COW
STORAGE
S
S = SCREW
LOOSEN FOR
DISASSEMBLY
2
1174
MODEL 1608
INITIAL PREPARATION
5112 J113 !
520
I
ANALOG OUTPUT
SWITCHES SHOWN FOR
OPERATION FROM 105-125V LINE
DiGi
:TAL
'UT
OUTF
J302
3
L‘IG”RE 7.
Exploded view Of Model 1600,16881\
4
0976
I
I
I
BATTERi FUSES
F203, F204
I
SPACER
(4 PLACES)
MODEL 1608 CHASSIS
CAUTION
DISCONNECT LINE CORD BEFORE OPENING
THE TOP AND BOTTDM COVER,
LINE VOLTAGE ON THE CHASSIS
REPRESENTS A SHOCK HAZARD.
FIGURE 8.
Installation "f Battery Pack.
\\
0976 5
INITIAL PREPARATION
MODEL 160B
SECTION 2.
GENERAL.
2-l.
needed for incoming inspecrian and preparation for
use.
INSPECTION. The Model 1603 was carefully in-
2-2.
spected both mechanically and electrically before
shipment. "pm receiving the instrument, check for
any obvious damage which may have occurred during
f*El"Sit.
TO verify the electrical specifications, follow the
procedures given in Section 6.
PREPAR**ION FOR "SE.
2-3.
ready-to-use.
line voltage or from rechargeable nickel-cadmium batteries (when the oprional Model 1688A Rechargeable
Battery Pack is installed).
How to operate From IdlIe Power.
a.
provides a three-wire cord which mates with third-wire
;rounded receptacles (see Figure 4 for ~1% configura--
tion,.
by wrapping the card around the base of the i"str"-
ment as shown in Figure 4.
the permanently installed line cord is stored
wow to Set Line Switches. The Made1 1608 has
1.
two rear panel Line Switches which enable selection
of line voltages over ranges from x0-llO", 105125v,
195-235", or 210-250". TO operate from line power.
determine the appropriate line voltage range to be
used and set the Line Swirches as fallows:
I
This section provides information
Report any damages to tne shipping agent.
The instrument can be powered from
TABLE 2-1.
Summary of Line Switch Settings.
‘Jo-110” I
The Model 160~ is shipped
The Model 16OB
LOW. 117
105-125” NORM, 117
I
For example, if the line voltage ea be used is
approximately 115 volts, select NORM and 117 which
permits B range of operarion from 105 to 125v.
hfter line Switches are set, connect the line cord
and set the Power Switch to LINE.
210-250"
195-235”
1
LO", 234
NORM. 234
INITIAL PREPARATION
b. Row to operate From Battery Power. TO operate
the Model 16OB from batteries, the Model 1688A Rechargeable battery Pack must be installed. The Model
1688A can be either field or factory installed.
batteries in the Model 1688A may need recharging be-
fare their first usage to power the Model 1600.)
The Model 1688A Rechargeable Battery Pack can
be insralled within the Model 1608 chassis at
any time.
Output is already installed, the Model 1688A
cannot be used simultaneously.
1. HOW to Install Model 168% Rechargeable Battery Pack.
1688A come already installed in the battery pack.
the battery pack includes 7 rechargeable "C" cells
(1.2", 3 AMP HR) and 1 rechargeable pack (16.8V).
If baeeeries need to be replaced or re-installed,
be certain to observe the proper polarity of individual cells as shown in Figure 6. To install the
Model 1688A Battery Pack, turn the instrument over
so that the bottom cover faces up. Loosen four
slotted screws on the batrom cover as shown in
Figure 4. (A chisel-blade screwdriver is requires'
to loosen the slotted screws.) Turn over the instrument with tap cover facing up, taking care to
hold the top and bottom covers together. Carefully
remove the top cover to gain access fo the printed
circuit board. (Two "ires that connect to the
Analog Oufput must be disconnected at the PC board
before the top cover can be set aside.) Check to
I
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
the cable oriented as sham in Figure 8.
4-wire Conneceor (5205) into the mating receptacle
(P205) taking care to orient the connector as
shown in Figure 8. After the Battery Pack is installed. replace the top cover. Turn over the instrumen; wiih bottom co&r facing up and tighten
down the four slotted-head screws.
Sumnary of nateerie Used in Model 1688A
However, if the Model 16028 Digital
The batteries furnished with the Model
(The
NOTE
Plug the
TABLE 2-2.
,.ine Fuse Requirements. The Model 1608 uses
2.
~VO line fuses to protect the line-operated power
SWPlY.
blow.
3. How to Replace Fuses in Model 1688A. The
!Jodel, 1688H uses 1 ampere fuses to protect the
power supply regulators in case of malfunction.
Fuses F203 and F204 are plug-in types and are located on pc board PC-349 as shown in Figure 8.
Keplace with 1 ampere, 3AB, slo-blo, Keithley Part
NO. FU-28.
6
ne fuse types are l/8 ampere, MB, slow-
Replace with Keithley Part No. F"-20.
Rechargeable "C" cell,
1.2". 2 AMP-FIR
Rechargeable battery
pack, 16.8V, .225
Am-m
1
TM-32
0976
The instrument must he operated in the BAT
mode in order t” obtain a valid battery condition 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.
GENERAL.
3-l.
needed to operate the Model 160B for measU*eme"f Of
voltage, cuirent, and resistance.
HOW TO SELECT POWER.
3-2.
powered from line voltage or rechargeable nickel-cadmium batteries ("hen the Model 1688A is installed).
The Model XOB has a built-in line-voltage power sup-
ply and line cord.
chargeable Battery Set is ordered and installed, then
the user has the oprion of selecting line or bateery
operation via the front panel rotary power switch.
The accessory Model 1688A Rechargeable Battery See may be ordered at ebe time of purchase of the Model 160B or may be purchased
and field installed at a later time if so
desired.
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.
Table 2-1.
1. Set rear panel Line Switches to appropriate
positions as show" in Figure 5.
This sec~ian provides information
The Model 160B may be
If the accessory Model 1604 Re-
NOTE
me Model 1688A features plug-in
OPERATING INSTRUCTIONS
see
HOW TO MAKE INPUT CONNECTIONS.
3-3.
has two front panel terminals identified as "HI"
(red) and '3.0" (black). These terminals accomodate
banana plugs. alligator clips, spade lugs, bare
wirea, and other similar input connections. Leads
may be fabricated using a good quality capper wire
terminated by single banana plugs such as Keichley
Part No. K-5 or dual banana plug such as Keithley
Part NO. m-7. Ready-made test leads are also avail-
able from Keithley. Accessory Model 1681 Clip-o"
Test Lead Set includes two 40 inch long leads terminated by a banana plug and spring-loaded clip which
easily attaches co wires and terminals on pc boards,
Model 1683 Universal Test Lead Kit features in-
etc.
terchangeable probe tips for various applications.
'I%e Kit includes regular probes, alligator clips,
banana plugs. spade lugs, and phone tips. All-cow==
leads and teminarions are best for measurements on
the lm" and ln ranges.
3-4. HO" TO SELECT FUNCTION. Function is selected
by means of a single front panel Range Switch. llie
Range dial is marked in "en&wring" units for meas-
"remenf Of voltage (rn", V), C"r*e"t ("‘4, LL4, n!A), and
resistance (‘2, kn, M0).
the knob clockwise causes the Model 160B to switch
to a less sensitive range.
For each function, rotating
The Model 1608
3. Set front panel Power Switch to LINE.
b. "cm to Operate from Battery Power.
Install Mode11688ARechargeable Battery Pack.
I .
2. Check battery voltages at Teat Points A and
B to ensure thaL batteries are charged sufficiently.
1. If necessary, plug line cord info ac power
and set Power Switch to CHG to bring battery "altage up to useable levels.
4. When bartery level is sufficient, disconnect
line cord and set Power Swifch LO BAT.
switch
POSition
OFF
LINE
CHG
BAT
Line Connected
1688A not installed
OFF
ON
OFF
OFF
a. DC “catage. The voltage sectors of the Range
Switch are designated in millivolts ("IV) and volts
I", for full ranees from lm" to 1000". A full stop
it'the 1000 "&range prevents inadverranr switching to the nanoampere ranges by clockwise rotation.
b, Resistance.
Lange Switch are designared in ohms (n), kilohms
(kn), and megohms (MO) for full ranges from 1 ohm
to 1000 megohms.
CU**e"t. The current sectors of the Range
C.
Switch are designafed in nanoamperes ("A), microamperes (,,A), and milliamperes (mA) for full ranges
franI 10 nanoamperes to 1000 milliamperes.
Condition of Instrument
Line connected
16888 installed
OFF
ON
ON
ON
The resistance sectors of the
Line not connected
1688~ installed
8
0976
POWER
S203
-ZERO
R114
- RANGE
SlOl
FIGURE 10. Front Panel Controls.
3-5. HO” TO ME‘“LS”RE “OLTIICE.
ures dc “aleage in seven ranges:
lV, lOV, LOO”, and 1ooov. Maximum dc input is 1200”
dc + peak ac.
a. How to Select Ra”E,e.
selected by rotating the Range Switch to the appropriate position.
in millivolts CmV); four positions are direct-reading in voles (VI. Decimal point is selected by the
Kan,qe Switch. Polarity is automatically displayed.
If the input signal exceeds twice full range, the
display blanks (3 least significant digits) to indicate an “overran& condition.
Range
SeCti”
1000 v
100 v
10 v
,
100 mv
10 mv
*Maximum allowable input is 1200” dc plus
peak ac even though display can be read
beyond 1.200”.
Three positions are direct-reading
“01
1 v
1 In”
TABLE 3-2.
1tage Ranges Displ;
Max. Display
1999 *
199.9
19.99
1.999
199.9
19.99
1.999
The Model 1608 meas-
Im”, lOnl”, loom”,
Function and range is
d
b. How to Determine Accuracy. The xodel 16011 nccuracy is iO.I% of readina f 1 dirit.
a display reading of 1.005 volt dc will have a” ,a,,certainty of 10.1% f 1 digit or r.002 volts.
put resisrance in the dc m”de is 10 o,c~“,,cs. !,eaiurements from relatively high source resistnnccs
could cause an additional reading error.
of error due to loading can bc determined by rhc
following relatiansbip:
% error = 100 x RS i (R, + 10’)
where R, = Source resistance in ohms
For example, a so”rcc resistance “f 10,000 ohms Viii
result in a loading error of approximately 0.1% ai
reading.
The input current of the 1608 Cal” also cause
reading errors on the nlOSL sensitive vo1cage
ranges when high source resistances are present. For example, an input CUrrent of lOpA
and a so”rce resistvnce of MI! produce a”
error voltage of loll”.
c. Maximum Allowable Input. The maximum L”P”L to
the Model 1608 is 1200” dc + peak ac. On lrn”, lOn,V,
and lOOn,” ranges,
6OOV (12OOV momentary) dc + peak ac. ‘,‘hc ?,odel ,,SO”
can display dc voltages greater tba” r120O” but dnmage to the input is possible.
the maximum conti”uox,s input is
For enarno1e.
The in-
The dln”“,:i
1174
0
OPERATING INSTR”CTIONS
MODEL L6OB
IMPORTANT
The Model 1608 provides ac rejection (NMRR)
of greater than 60 dB on the highesf range.
However, a large ac signal superimposed on
a dc level could cause damage if the input
CO the Model 160" exceeds 1200 volts dc +
peak UC.
d. How to Zero the Display. To accurately zero
the instrument, place a low-thermal short (such as a
piece Of clean copper wire) across the input rerminals, set Lhe Range Switch to the lm" range, and adjust the front panel Zero conerol for a flashing "i"
sign at the display.
The display should then read
t.OOO, with some flicker of the least significant
digit due to noise and A-D converter uncertainfy.
Once the zero has been set accurately, there should
be little reason to rezero the instrumenf again soon
when making measurements on the 10~1" through 1000"
ranges. The time stability of rhe zero setring is
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.
A test set-up and cables when connected to the 160B
may cause offset voltages because of thermoelectric
effects (see section 3-9). These offset voltages
might be only a few microvolts or several tens of
microvolts. In such situations, the Zero control
can be used to buck out any initial offsefs.
I.""
thermal cabling and connections should be used whenever possible. The instrument zero can also be check
ed, and adjusted, by shorring the input on any range
(voltage, current, or resistance).
me zero c**t*01
will have varying effects on the differenr ranges
depending on the sensitivity of the input amplifier,
but the zero control can be used in this manner.
Again, it should be emphasized, that for most meas-
"remene~ with the Model 160B, the Zero control can
be set once and then left untouched. (See also ?ec-
tion 3-6c "LO" Ohms Zeroing").
NOTE
With the input open 0" the lm" Range, the
Model 160~3 display may show a reading as
high as i.100. This 19 equ*va1ent to an
offset currene of lo.opA.
If the display
shows a reading grearer than t.100, then
the internal potentiometer, R121, should
be readjusted. Typically, ehe offset current will be less than 5p~.
HOW TO MEASURE RESISTANCE. The Model 1608
1-6.
measures resistance in 10 ranges: lsr, 1on, 10011,
Ikn, IOk&?, lOOk0, IM,,, lOMn, lOOK,, and 100011!2.
a. HO" to Select Range.
Function and range is
selected by rotafinf: the Ranae Swifch LO rhe BPPTOpriate position. Three posi;ions are direct-reading
in ohms (n): three positions are direct-reading in
kilohms (kn); four positions are direct-reading in
megohms (MQ) Decimal point is selected by Range
Switch. If the input signal exceeds twice full range,
the display blanks to indicate an "overra"& condl-
ti**.
TABLE 3-3.
Resistance current Ranges
Range Max. Impressed
setting LIiF3play units current
1. n 1.999 ii I InA
10 n 19.99 n lti
1 MI1 1.999 Mn 100 “A
10 Mn 19.99 MO 10 "A
100 Mr! 199.9 Mn I"‘4
1000 M* 1999 MO 0.1 "A
b. How to Determine Accuracy. The accuracy of cbe
Model 1608 is specified in terms of a nercen~ of
reading and a p¢ of range. For example, a display of 1.000 kilohID (kn.1 will haw an uncertainty
of ~0.004kQ.
C. HO” to Measure “LOW” ohms. when making measurements on the ln, lOn, and 1OOn ranges, rhe Model
160B is to be zeroed on the IQ range. The zeroing
is accomplished by shorting the test leads together.
and adjusting the display for a flashing + and -
.ooon. By zeroing the instrument in this manner,
lead resistance of 200 mill.iohms (minimum) can be
compensated for. The instrument must be rezeroed on
the lil range each time a different set of iese leads
is used. Before making meaS"reme"tS right *t the input rerminals (no test leads used), rhe instrumene
should be zeroed on the iii Range after placing a
short, such as a piece of copper wire, across the
binding posts. Copper leads and clips are best for
making measurements on the ln Range, because the
voltage drop across a In resistor is only Im".
CAUTION
e. 80" to "se Model 1601 AC/DC Probe.
measuremenfs, connect the Model 1601 accessory K/DC
Probe to the Model 1608 inpur terminals.
Range to desired voltage range.
to AC.
"se the probe tip plus ground clip to make
Set switch on probe
connections to circuit under eesc.
complete specifications.
f.
How to "se Model 1682 RF Probe.
measurements, connect the Model 1682 Probe to the
Model 160B input terminals.
Set the Range to desired
TO make ac
Set the
see section 5 for
To make rf ac
voltage range. Maximum allowable input is 30" *Ins
ac, 200” dc.
10
Care should be taken when making resistance
measurements in circuits which may have voltages on capacitors, etc. or "here line voltage is present. Although the Model 1608 is
fully protected against accidental voltages
up to 250" rms in resistance function, if
higher voltages are applied, damage may occur.
1174
-FUSE SHOWN FUSE SHOWN
TWICE ACTUAL SI
Range Max.
setting IDisplay Units
I,0 nA 19.99
100 nA 199.9
LO
100
1
1.
LB.4
,lh
UA
InA
1.999 II‘4 1040
19.99
199.9
1.999 n!A 10 il
Il.4
IL4
irA
UA
s,,une R*
10 rnA 19.99 In.4 I. 0
100
1000
lx.4
mi\
199.9 mA 0.1 !1
1.999
ti
1060
10%
10311
10%
0.1 G
OPERATING INSTR”CTIONS
MODEL 160B
d. HOW to "se the Model 1651 Current Shunt (for
meaS"remenfS to SOA). current measuremenf capability
Of the Model 160B may be extended to 50 amperes
through ctle use Of accessory Model 1651 SO-Ampere
shunt.
The Model 1651 permits 4-terminal connections
to minimize meaeuremene error.ciue to lead resistance.
To use the Model 1651, connect the voltage sensing
leads eo the Model 160B input terminals. Connect
separate current leads (not furnished) beuveen xhe
source and the large hex-head bolts on the Model 1651.
The current leads should be rated for currents up to
50 amperes. me Shunt resistance is 0.001 ohm, vhich
produces a sensitivity of lmV/Amp. As examples, 10
amps current results in a lOIn" drop on 1Oln" RANGE,
and 30 amps yields a voltage drop Of 3Oln" which can
be read on the loom" RANGE. Power diss*paCed in the
shunt is 2.5 watts at 50 amperes.
3-8. NOISE CONSIDERATIONS.
The 1imic of resolution
in voltage and current measurements is determined
largely by rhe noise generated in the source. stray
low-level noise is present in some form in nearly al1
electrical circuits. The instrument does not distin-
guish between stray and signal voltages since it measures the net "olfage.
when using the lnl" and 1omv
ranges, consider the presence of low-level e1ectrical phenomena such as thermocouples (thermoelectric
effect), flexing of coaxial cables (triboelectric
effect), apparent residual charges on capacitors
(dielectric absorption), and battery action Of t"O
terminals (galvanic action).
3-11. AC ELECTRIC FIELDS. The presence of electric
fields generated by power lines or other sources can
have an effect on instrument operation. AC voltages
which are very large with respect to the full-range
sensitivity could drive the input amplifier into saturarion, thus producing an errOneo"S DC OUtpUt. At
line frequency or twice line frequency, the insLrument is capable of rejecting AC voltages whose peak-
to-peak amplitude is equal to the full-range DC sell-
sftivity on the loom" through 1OOOV ranges. This
level of interfering AC signal will produce no more
than 1 digit error.
On the lm" and 1OmV Ranges, the
instrumenf can reject line frequency and twice line
frequency signals whose p-p amplitude is equal CD 10
eimes the full-range sensitivity. Far example, on
rhe ID," Range, a 1OmV p-p, 50 Hz signal will produce
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 fullrange sensitivity on the lln" and 1omv ranges will
cause clipping in the AC section of the Model 160B
input amplifier.
For this reason, shielding is re-
com,,,ended when making sensieive DC voltage measure-
menrs, or when making measurements from high so"rce
impedances.
(See Shielding, Section 3-12.) The inserunlent is also capable of rejecting frequencies
other than power line frequencies.
There is one problem to consider; however, the input amplifier of the
Model l6OB uses a modulator to convert DC signals LO
AC signals before amplification. The drive frequency
of this modulator is 220 HZ nominally, f approx. 5%.
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
potentials) are generated by thermal differences between two junctions of dissimilar metals. To minimize the drift caused by thermal emfs, "se copper
leads to connect the circuie to the instrument. The
front panel ZERO control can be used to buck out a
cmstant thermal offset "aleage if necessary. The
Keithley accessory Model 1483 La" Thermal. Connecrio"
Kit contains all necessary materials for making very
low thermal copper crimp connections far minimizing
thermal effects.
3-10.
MAGNETIC FIELDS.
The presence of strong magnetic fields can be a potential sw.,rce of ac noise.
Magnetic flux lines which CUt a conductor can produce
large a-c noise especially at power line frequencies.
The voltage induced due to magnetic flux is propor-
tional fO the area enclosed by the circuit as well
as the rate of change of magnetic flux. For example,
the motion of a 3-inch diameter loop in the earth's
magnetic field Will induce a signal of several tenths
of a microvolt.
one way to minimize magnetic pickup
is to arrange all wiring so that rhe loop area enclosed is as small as possible (such as twisting inpur leads). A second way co minimize magnetic pickup
is to use shielding as described in Section 3-12.
3-12. SHIELDING.
a. Electric Fields. Shielding is usually necea8arv when the insrrument is in the eresence of verv
l&e a-c fields or when very sensi;ive measuremen;s
are being made. The shields of rhe measurement circuit and leads should be connecee* together to ground
at only one point.
This provides a "tree" configura-
tion, which minimizes ground loops.
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 circuit, the lead wires, or the instrument itself.
C. Other Considerations.
1. Voltmeter Measurements. Use shielded input
leads when source resiseances are greater than 1
kilohm or when long input cables are used.
2. Current Measurements. On the mA and PA current ranges, no special shielding precautions need
be taken. However, an the 100 and 10 nanoampcre
ranges, shielded input leads are recommended.
3. llesiatance Measurements. Shielding of input
leads and source are recommended for measurements
on the 10 megohm through 1000 megohm ranges to prevent errOneO"S readings.
12
1174
FIGURE 12.
Voltage Measurements Using Model 1601 AC/DC Probe.
CURRENT TERMINALS
VOLTAGE TERMINALS
1
1174
;*
VOLTAGE LEADS
FURNISHED
OPERATING lNSTR"CTlONS
I
i+
--~ EXTERNAL
MODEL 1608
MODEL 1608
E%'
DC
FIGURE 14.
3-13. HOW TO USE THE ANALOC
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.
analog output enables the Model 1608 to be used as
a la"-noise, low drift DC amplifier.
TABLE 3-5.
hi" at liNALOG OUTPUT
Range
1 In"
1.0 rn"
100 In"
For off-ground operarim, the analog output should
be connected only to equipment capable of operating
off-ground also.
is at the same poeential as the "LO" input terminal
of the Model 160".
3-14. HOW TO USE MODEL 1608 OFF-GROUND. The "LO"
terminal can be operated off ground at potentials
Of up tLl 11200".
to power line ground is specified at lOOOMn, or 10'0
(shunted by 300@).
tance from I.0 to GNE is two decades greater than
log!? (lO"O).
operating the Model 1608 off ground results in very
1.itr1e loading (from LO to GNU) of a floating source.
AC 1000" above ground, the Model 1608 will require,
typically, only 1Onh from the source.
i.solation also accounts for the high common-mode re-
x1000
x100
x10
The low side of the analog output
Isolation franI ehe "LO" terminal
Ty,,ically, the isolation resis-
Because of this excellent isolation,
Gain
OUTPUT.
Full Range
The Model 16OB
Also, the
OUtpUt
1"
1"
1"
The
excellent
CASE 8'
GROUND
Floating Operation
"across lk
The "isolation" capacitance from LO to GNC is impor-
tant when AC common-mode signals are present. in
the Model 1608, rhis capacitance is specified at 300
pF maximum.
has a reactance of approximately 10Mli. With the HI
terminal driven and a source impedance of lkll, R
1OOOV p-p, 60 Hz, common-mode signal will produce a
voltage of only loom" p-p across the Model 1608 in-
put terminals. This lOOmV p-p signal will be lurtbcr
rejected by the input amplifier and A-1) converrer SC
that the total rejection at the digital display is
at 1easL 140 LIB. At lower levels of *C common-mode
signals, the total rejection at the display is even
greater.
should produce only about 1 digit errur on the lh"
Range for a total rejection of approx. 160 dR. (IiT
driven, IkQ source impedance.1 WiCh both AC and IDC
common-mode signals, rejecti,, is lnuch greater than
specified when the Model 160B LO terminal is driven,
rather than the HI rerminal. Where there is a need
for even greater isolation from LO (0 power Line
ground, or where there is a need fo float at porcn-
tials greater than UOO volts above power Line ground
the Model 1688A Battery Pack should bc used.
TYPICAL
>lO"n ISOLATION
I
At a frequency of 60 HZ, 300 picofarads
For example, a 60 Hz, 100" p-p signal
RESISTANCE
= I x lkn = 10-a x 103 = lOll"DC
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 sinking f15 milliamperes).
REMOTE CONTROLS:
Strobe: 6 lines for serializing in multiples Of 4
bits. Logic "1" inhibits controlled OUtpUt lines.
i’
O"t"UC Hold:
ing af DigitLOutput.
Display Hold:
reading (escept far polarity and decimal) at
“igital output and Display.
0976
I.oeic "0" retains data from last read-
Logic “0” retains data from last
15
CwmATING INSTR”CTIONS
MODEL 160B
3-15.
HOW TO USE MODEL 16028 DIGITAL OUTPUT.
a. General.
FIGURE 16.
The Model 16028 Digital Output provides
Exploded View of Model 1608/1602B
binary-coded decimal (BCD) ouepufs and several control
inputs.
installed" or "field-i"srallable".
2his accessory is available either
The Model 1602B
"fsctary-
consists of a single printed circuit baard (K-352)
with input and integrally mounted "u~pue ca""ecfar,
and an ouf,,"t mating cm,ne~tc,r with hoad.
b. Installation of Model 1602B.
The Model 16028
ia installed inrernal to the Model 160B and is DOW~Ied by the Model 1608 line operated power supply:
NOTE
It is not ineended
used simulta"eously with the Model
that the Model 16028 be
1688A
Battery Pack. To use the Model 1602B. the
Model 1688A muse be remaved and set aside.
It is possible, however, for the u8er eo
make his own wiring modifications 8" that
the
Model 1688.4 Battery Pack can power rhe
Model 160B while lacated outside the Made1
160B.
DISCONNECT LINE COBB BEFORE OPENING
THE TOP AND BOTTOM CO"ER.
LINE VOLTAGE ON THE CHASSIS
REPRESENTS A SHOCK HAZARD.
CAUTION
To install the Model 16028. turn the Model 160B "ver
so mar: me DOttOm cover races up. Locate and loose”
.
four slotred scre"s as shown in Figure 4. The 8cre"B
are "captive" and should "at be completely removed.
Once the screws are loosened,
covers ragether and turn Wodel 1608
CO"Br- is up.
Carefully lift off rhe top c"ver and
disconnect the wires to the Analog Output.
hold
top and bott"m
so chat the top
Locate 16-
pin receptacle 5201 o" the ma,." circuit board W-349).
Plug the mating c""necLor (P301) from the Model 1602B
into 5201, after checking that pin numbers are corresponding. Locate Spin plug P208 on the main circuit
b"ard (PC-349).
P208.
Be sure that the
"A" af 5303.
Connect 5303
from the Model 1602B to
“A”
of PZOE lines up with the
Place Model 1602B board o" four spacers
with cables positioned as shown in Figure 17. Rem"ve
digital-output c"ver plate fram Model 160B fop c"ver.
Place t"p c"ver back on instrument, after reconnecting
Amlog output wires. Turn instrument 0"e-L and tighten
four slotted screws.
C.
Pi" Idenrif*cae*on of FleaI? Panel Digital OutpUt
connector.
(5302)
external equipment.
The Model 1602B uses a 37-pin connector
Co provide all input and output connections to
Pins are identified as shown in
Table 3-7.
16
0976
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