Keithley AUTO-PROBE 167 User manual

INSTRUCTION MANUAL
MODEL 167
AUTO-PROBE™
DIGITAL MULTIMETER
ICEITHLEY irsrSTRU]VnEIS:TS

WARRANTY
We warrant each of our products to be free
from defects in material and workmanship. Our
obligation under this warranty is to repair or
replace any instrument or part thereof which,
within a year after shipment, proves defective
upon examination. We wi ll pay domestic
surface freight costs.
To exercise this warranty, cal l your local
field representative or the Cleveland factory,
ODD 216-248-0400. You wil l be given assist
ance and shipping instructions.
REPAIRS AND RECALIBRATION
Keithley Instruments maintains a complete re
pair service and standards laboratory in Cleve
land, and has an authorized field repair facil ity
in Los Angeles and in al l countries outside the
United States having Keithley field repre
sentatives.
To insure prompt repair or recalibration serv
ice, please contact your local field representa
tive or the plant directly before returning the
instrument.
Estimates for repairs, normal recalibrations,
and cal ibrations traceable to the National Bu
reau of Standards are avai lable upon request.

INSTRUCTION MANUAL
MODEL 167 AUTO-PROBE™
DIGITAL MULTIMETER
Copyright Keithley Instruments, Inc.1972
0172

CONTENTS
Title Page i
Contents ii
List of Illustrations iii
Specifications iv
1. General Information 1
1-1. Introduction . 1
1-2. Warranty Information 1
1-3. Change Notice 1
1-4. Applications 2
1-5. Accessories 2
2. Initial Preparation 3
2-1. General 3
2-2. Inspection 3
2-3. Preparation for Use 3
3. Operating Instructions 4
3-1. General 4
3-2. Turn-on Procedure 4
3-3. Connections 4
3-4. Function Selection 6
3-5. Operation as a Voltmeter 6
3-6. Operation as an Ohmmeter 8
3-7. Operation as an Ammeter 10
3-8. Battery Operation 12
3-9. Line Operation 14
3-10. Auxiliary Power Operation 14
3-11. Battery Life 14
3-12. Display 16
4. Theory of Operation 18
4-1. General 18
4-2. Analog Circuitry 19
4-3. Digital Circuitry 20
4-4. DC Voltage Operation 25
4-5. AC Voltage Operation 26
4-6. OHMS Operation 27
4-7. Power Supply 28
5. Maintenance 29
5-1. General 29
5-2. Required Test Equipment. ... . ... 29
5-3. Performance Checks 29
5-4. Adjustment and Calibration Procedure . 33
5-5. Troubleshooting 41
5-6. Battery Test 41
5-7. Battery Replacement 41
5-8. Battery Charging 42
6. Replaceable Parts
6-1. General 45
6-2. Ordering Information 45
6-3. Cross Reference. 47
6-4. Parts List 48
6-5. Code-to-Name List. 63
7. Schematic Diagrams 65
7-2. Block Diagram, No. 25354D 67
7-3. Power System, No. 25340D 68
7-4. Analog Circuitry, No. 25342D 69
7-5. Digital Circuitry, No. 25343D 70
Appendix
A. Service Form
B. Change Notice
0172

MODEL 167
ILLUSTRATIONS
ILLUSTRATIONS
Figure No.
Title Page No.
1 Front Panel with Probe Installed
1
2 Front Panel with Probe Removed 5
3
Rear Panel, Auxiliary Power Receptacle
5
4
Operation as a Voltmeter 7
5
Operation as an Ohmmeter
8
6
Measurement of Diode Resistance
9
7
Operation as an Ohmmeter
10
8
Digital Display 11
9
Battery Installation 13
10
Battery Compartment
15
11
Overall Block Diagram 18
12 Full Wave Rectifier
19
13
LSI Block Diagram
21
14
A/D Converter Block Diagram
21
15
Identification of Segments
24
16
Identification of Multiplex Lines
24
17
DC Voltage Operation
25
18
AC Voltage Operation
26
19
OHMS Operation
27
20
Top Cover Assembly
34
21
Chassis Assembly
35
22
Calibration Controls
37
23
Auxiliary Power & Battery Check
43
24
Test Points on Circuit Board
44
25
Component Layout, Resistors
53
26
Component Layout, Capacitors
54
27
Component Layout, Transistors
55
28
Printed Circuit PC-307
56
29
Case Outlines
57
30
Case Outlines
58
31
Case Outlines, Resistor Networks
59
32
Case Outline, LSI-1
60
33
Probe Assembly
61
0172

SPECIFICATIONS
MODEL 157
SPECIFICATIONS
AS AN AUTORANGING DC VOLTMETER
RANGE: + 1 millivolt per digit to +1000 volts.
ACCURACY: +0.2% of reading +1 digit
INPUT IMPEDANCE: 55 megohms shtmted by approximately 220 picofarads.
NMRR: Greater than 55 dB above 50 Hz.
AS AN AUTORANGING AC VOLTMETER
RANGE: 1 millivolt per digit to 500 volts rms.
ACCURACY: Up to 200 volts; +1% of reading +2 digits, 20 Hz to 10 kHz, +2% of
reading +A digits to 20 kHz. 200 volts to 500 volts; +2% of reading +2
digits, 20 Hz to 1 kHz, +5% of reading +4 digits to 20 kHz.
INPUT IMPEDANCE: 50 megohms shunted by approximately 220 picofarads.
AS AN AUTORANGING OHMMETER
RANGE: 1 ohm per digit to 20 megohms.
ACCURACY: +0.3% of reading +1 digit +1 ohm.
TEST CONDITIONS: Current; I milliampere to 0.1 microampere depending on range.
Voltage; 1 volt at 1000 digits, 9 volts maximum into an open circuit.
GENERAL
READING TIME: Less than 2 seconds to rated accuracy.
DISPLAY: 3 1/2 digits, appropriate decimal position, polarity indication and
indication of function (DC, AC, k(2, MO) all on probe. Upranges at 2000, down-
ranges at 0189.
POLARITY: Automatic
RANGING: Fully automatic on each function.
OVERLOAD INDICATION: Display blinks when beyond specified maximum range.
MAXIMUM OVERLOAD: 1200 volts dc + peak ac on voltage ranges.
130 volts dc + rms ac on ohms.
STABILITY: +0.02% of reading +0.2 digit per °C. Calibrated (? 23°C.
ENVIRONMENT: Operating 0°C to 50°C. 0% to 70% Relative Humidity up to 35°C.
Storage -25°C to +65°C.
POWER:
Supplied
with
Model
6 "D" Cells for
internal mounting
(Any type useable)
Life with
continuous
operation
Life with
push-to-
read switch*
167
Alkaline
20 hours typ.
3 months typ.
167/1671
N icke1-Cadmium
12 hours **
per charge typ.
1 month per
charge typ.
^Holding probe turns ins^trument on. Instant warmup permits final reading
within 2 seconds.
**Recharging of internal Nickel-Cadmium batteries and/or line operation is
provided by power source included in Model 1671.
BATTERY TEST: Test point for measuring battery voltage with instrument itself
provides indication of battery condition.
CONNECTORS: Probe tip and alligator ground clip. When probe is stored in
instrument, banana jacks.
DIMENSIONS, WEIGHT: Probe; 7-3/8 in. x 5/8 in. (188 x 15mm), 1-1/4 in. x
3/4 in. (31 X 18mm) display area, 4-1/2 ft. (1500mm) cable. Electronics
Pack; 3 in. high x 6-3/4 in. wide x 10-1/2 in. deep (75 x 170 x 265iim) , net
weight (with Alkaline cells) 4 pounds (1,9 kg).
ACCESSORIES FURNISHED: Ground lead, attached probe.
0172

MODEL 167
GENERAL INFORMATION
SECTION 1.
GENERAL INFORMATION
I-I. INTRODUCTION. The Model 167 is a compact, versatile, autoranging digital
multimeter useful for measurement of voltage, resistance, and current. The
Model 167 indicates ac volts from 1 mV to 500 volts, dc volts from 1 mV to 1000
volts, and resistance from Ifl to 20 MSI. Current measurements also can be made
fromO.l pA to 2 amperes with the accessory Model 1673 Current Shunt.
1-2. WARRANTY INFORMATION. The warranty is given on the inside front cover
of the manual. If there is a need for service, fill out the Service Form sup
plied at the back of the-manual.
1-3. CHANCE NOTICE. If there are any improvements or changes to the instru
ment not incorporated into the manual these will be explained on a yellow
Change Notice attached to the inside back cover.
167 AUTO PBOBl DMIVI
FIGURE 1. Front Panel With Probe Installed.
0172

GENERAL INFORMATION
1-4. APFLICAXrONS.
MODEL167
a. Probe Measurements. The Model 167 Is useful for electrical measure-
ments wherever a portable battery-operated instrument is needed. Since the
digital display is in the probe, measurements can be quickly and easily made
by simply moving the probe from point-to-point such as when servicing elec
trical circuits.
b. Bench Measurements. The Model 167 is also useful as a bench operated
multimeter with the probe installed in the front panel. The front panel ter
minals are used to make all connections for normal multimeter operation.
1-5. ACCESSORIES.
a. Model 1671 Rechargeable Battery Kit. This accessory includes a set of
six nickel-cadmium batteries and line-operated Recharger. The Recharger cable
mates with the rear panel "AUXILIARY POWER" receptacle on the Model 167. The
Model 167 can be operated while the Recharger is connected to line power. The
Recharger provides greater than 10® ohms insulation resistance between LO and
power ground with 500 volts maximum common mode voltage.
b. Model 1672 Line Adapter. This accessory converts the Model 167 to line
operation. The Adapter cable mates with the rear panel "AUXILIARY POWER" re
ceptacle on the Model 167. The Model 167 automatically switches to battery
power if the line voltage is interrupted. The Adapter provides greater than
10® ohms insulation resistance between LO and power ground with 500 volts max-
imum common mode voltage.
c. Model 1673 Current Shunt. This accessory is a current shunt which adds
to the Model 167 the capability to measure current from 0.1 pA to 2 amperes.
Accuracy of the shunt resistors is +0.37.. The resistors are switch selected in
decade steps from 1 ohm to 10 kilohms.
d. Model 1674 Carrying Case. This accessory is a rugged leather carrying
case with an adjustable shoulder strap and belt loop.
e. Model 1677 Power Cable. This accessory is a power cable which mates with
the rear panel "AUXILIARY POWER" receptacle. The 4 foot long cable permits
convenient connections to an external power source.
f. Model 1678 Rechargeable Battery Set. This accessory is a set of six
nickel-cadmium batteries without Recharger.
g. Model 1679 Alkaline Battery Set. This accessory is a set of six non-
rechargeable alkaline cells.
0172

MODEL 167 INITIAL PREPARATION
SECTION 2. INITIAL PREPARATION
2-1. GENERAL. This section describes procedures for Incoming Inspection and
preparation for use.
2-2. INSPECTION. The Model 167 was carefully Inspected both mechanically and
electrically before shipment. Upon receiving the Instrument check for any
obvious damage which may have occurred during transit. Report any damages to
the shipping agent. To verify the electrical specifications test the Instru
ment using the Performance Check procedure In Section 5.
2-3. PREPARATION FOR USE. The Model 167 Is shipped ready-to-use with six
alkaline batteries Installed In the battery compartment. The probe Is Installed
In the front panel with the cable wrapped around the base of the chassis. The
ground lead Is stored In the opening on the bottom of the Instrument.
a. Battery Operation Using Alkaline Cells. The Model 167 Is useable for up
to 20 hours of continuous operation from a set of six alkaline batteries. The
battery condition may be checked at any time using the probe for a self-test.
To test the batteries, remove the probe from the front panel, depress the "DCV"
pushbutton and "push-to-read" switch along the top of the probe. Touch probe
tip to the rear panel "BATTERY TEST" terminal and read the display. The read
ing should be greater than 6 volts for satisfactory battery condition. If the
Model 167 falls to turn on, check for proper Installation of the batteries as
shown In Figure 9. If the voltage Is too low, replace with new batteries as
explained In paragraph 3-8c.
b. Battery Operation Using Nickel-Cadmium Cells. The Model 167 can also be
powered by rechargeable nickel-cadmium batteries for up to 12 hours continuous
operation. The battery condition may be checked at any time using the probe for
a self-test. To test the batteries, remove the probe from the front panel, de
press the "DCV" pushbutton and "push-to-read" switch along the top of the probe.
Touch probe tip to the rear panel "BATTERY TEST" terminal and read the display.
The reading should be greater than 7 volts for satisfactory battery condition.
If the Model 167 falls to turn on, check for proper Installation as shown In
Figure 9. If the batteries are Installed properly and the voltage Is too low,
connect the accessory Model 1671 Recharger as described In paragraph 3-8d and
recharge the batteries. To ensure that the nickel-cadmium batteries are fully
charged, recharge the batteries at least 16 hours. Since the Model 1671 Re-
charger Is useable as a line power adapter, the Model 167 can be operated con
tinuously even while recharging the batteries.
c. Line Operation Using the Model 1672. The Model 1672 converts the Model
167 to line operation when connected as described In paragraph 3-9.
0172 3

OPERATING INSTRUCTIONS MODEL 167
SECTION 3. OPERATING INSTRUCTIONS
3-1. GENERAL. This section describes the procedures for operating the Model
167 as a voltmeter, ohmmeter, and ammeter.
3-2. TURN-ON PROCEDURE. When the probe is installed in the front panel the
Model 167 can be turned on by depressing any one of the front panel push
buttons identified as "ACV", "DCV", or "OHMS". When the probe is removed
from the front panel the "push-to-read" bar along the top of the probe must
be depressed and held in this position to turn on the instrument. The display
in the probe is lighted whenever the instrument is turned on and therefore
serves as a "power on" indication. When the "push-to-read" bar on the probe
is released the instrument will be turned off thereby conserving battery
power. When the probe is installed in the front panel the Model 167 will be
turned on continuously unless the front panel "OFF" pushbutton is depressed.
3-3. CONNECTIONS. The Model 167 has two front panel terminals identified as
"HI" (red) and "LO" (black). These terminals mate with "banana" plugs similar
to Keithley part no. BC-5. The probe tip can also be used for connections to
"HI" instead of the front panel "HI" terminal.
a. Probe Measurements. The Model 167 probe can be used for in-circuit meas
urements with the convenience of a display visible right at the point of meas
urement. To make a measurement, remove the probe from the front panel, unwind
the probe cable, select the desired FUNCTION, depress the "push-to-read" bar,
and use the probe and front panel "LO" terminal for input connections. When
the probe is used for measurements the front panel "HI" terminal is automati
cally disconnected. The accessory ground lead, which is stored in the bottom
of the instrument, may be used for connection to the "LO" terminal.
b. Bench Measurements. The Model 167 can be used for making measurements
with both front panel "HI" and "LO" terminals connected to the input. To make
a measurement, install the probe in the front panel and select the desired
FUNCTION. The front panel "HI" is activated only when the probe is installed
in the front panel opening designated "PROBE". The accessory ground lead may
be used for connection to the "LO" terminal. A similar lead may be used for
connection to the "HI" terminal. Since the front panel terminal spacing is
3/4", a dual "banana" plug (such as Keithley part BC-7 ) may be used for quick
connections to both terminals.
0172

MODEL 167
OPERATING INSTRUCTIONS
PROBE INSERTED
FOR BENCH USE
PROBE TIP "
IS INPUT "HI"
"LO" CLIP LEAD STORED
IN BOTTOM PANEL
TO TURN-ON, DEPRESS
TOP OF PROBE
FRONT PANEL
TERMINALS
CABLE UNWINDS
TO FIVE FEET
DISPLAY IN PROBE
FIGURE 2. Front Panel With Probe Removed.
\
FIGURE 3. Rear Panel, Auxiliary Power Receptacle.
0172

OPERATING INSTRUCTIONS MODEL 167
3-4. FUNCTION SELECTION. Four front panel pushbuttons are used for selection
of ac volts (ACV), dc volts (DCV), resistance (OHMS), or power off (OFF).
NOTE
When any one pushbutton is depressed, all three remaining buttons are
released. However, a condition may exist where all four buttons are
released. This condition is a non-useable mode where the input "HI"
is disconnected and the display indicates 0-0-0 kfl. If this occurs,
depress the desired function.
3-5. OPERATION AS A VOLTMETER. The Model 167 can be used to measure ac or
dc voltage from 1 mV to 500 Vac or to 1000 Vdc.
a. DCV Operation. The Model 167 automatically indicates dc voltages from
1 mV to 999V with polarity automatically indicated.
1. Measurement Procedure. Depress the "DCV" pushbutton to select dc volt
age measurements. Make input connections using the probe or front panel "HI"
and "LO" terminals as described in paragraph 3-3. Depress the "push-to-read"
switch to turn-on the display. The digital display is described fully in
Figure 8 and the caption below the illustration.
NOTE
The Model 167 automatically ranges to the proper range with decimal
point and polarity automatically indicated. A lighted "minus" sign is
displayed for negative dc voltages. A positive polarity is not indicated
but is implied when the "minus" sign is turned off.
2. Input Impedance. The input resistance is 55 megohms over the entire
voltage range. The shunt capacitance is approximately 220 picofarads. The
high input resistance allows measurements to be made without significant
circuit loading errors.
3. Accuracy. The Model 167 accuracy is specified as +0.2% of reading +1
digit over the entire voltage range.
4. Maximum Input. The maximum input voltage which can be applied is
specified as 1200V (dc + peak ac). The Model 167 display flashes when the
input exceeds +999 volts although the reading will be displayed up to the
maximum dc input.
0172

MODEL 167
OPERATING INSTRUCTIONS
b. ACV Operation. The Model 167 automatically indicates ac voltages from
1 mV to 499 volts over a range of frequencies from 20 Hz to 20 kHz.
1. Measurement Procedure-. Depress the "ACV" pushbutton to select ac volt
age measurements. Make input connections using the probe or front panel "HI"
and "LO" terminals as described in paragraph 3-3. Depress the "push-to-read"
switch to turn-on the display. The digital display is described fully in
Figure 8 and the caption below the illustration.
NOTE
The Model 167 automatically ranges to the proper range with decimal point
automatically indicated.
2. Input Impedance. The input resistance is 50 megohms over the entire
voltage range. The shunt capacitance is approximately 220 picofarads.
3. Accuracy. The Model 167 is an average-reading meter which is calibrated
in terms of the rms value of a sine wave. The basic accuracy is +1 "L of
reading! 2 digits (up to POOV, 20 Hz to 10 kHz).
4. Maximum Input. The maximum input voltage which can be applied is
specified as 1200V (dc + peak ac). The Model 167 display flashes when the
input exceeds 499 volts rms although the reading will be displayed up to
the maximum allowable input.
DCV FUNCTION
POIARITY FUNCTION f
FIGURE 4. Operation As A Voltmeter.
0172

OPERATING INSTRUCTIONS
MODEL167
3-6. OPERATION AS AN OHMMETER.
from 1 ohm up to 20 megohms.
a. Measurement Procedure.
D
The Model 167 can be used to measure resistance
epress the "OHMS" pushbutton to select resistance
Make input connections using the probe or front panel "HI" and
Depress the "push-to-read" switch
and
measurements.
"LO" terminals as described in paragraph 3-3.
to turn-on the display. The digital display is described fully in Figure 8
the caption below the illustration.
NOTE
The Model 167 automatically ranges to the proper range with the decimal
point indicated automatically. The appropriate range symbol (either kfl
or Mfi) is indicated automatically by the "lighted bar" adjacent to either
the kn or Mfl symbol.
b. Test Current. The Model 167 delivers a test current from 0.09 pA to
0.9 mA as shown in Table 3-A. The "LO" terminal is positive with respect to
the "HI" terminal. The terminal voltage is approximately 1.8 volts for a max
imum reading on any range. The maximum open circuit voltage is approximately
9 volts in series with 50 megohms.
c. Accuracy. The Model 167 accuracy is specified as +0.37. of reading +1
digit +1 ohm.
d. Maximum Input. The maximum input voltage which can be applied to the
input when in the "OHMS" mode is 130V dc or ac rms. If this voltage is exceeded
and connected for more than a few seconds, overheating of the range resistors
may occur with subsequent change to the accuracy.
OHMS FUNCTION
OBSERVE POLARITY APPLIED
FIGURE 5. Operation As An Ohmmeter.
0172

MODEL 167
OPERATING INSTRUCTIONS
e. Diode Test. When measuring the forward resistance of a semiconductor
junction (such as a diode) connections should be made as shown In Figure 6a.
Two different readings can be displayed depending on the manner In which the
measurement Is made. The reverse resistance for a silicon junction should
indicate greater than 20 megohms when connected as shown In Figure 6b.
1. Short Circuit Technique. Connect the diode and shorting switch (or
shorted leads) as shown In Figure 6a. To make a reading, remove the short
across the terminals. The display should Indicate less than 1000 ohms for
for a typical silicon diode. This technique Is recommended when checking
diode conduction.
2. Open Circuit Technique. Connect the diode as above except do not short
the Input terminals. The display should indicate less than 5 megohms when
making a forward resistance measurement of a silicon diode.
DIODE
(Open switch to read.)
FORWARD RESISTANCE
(6a)
DIODE
REVERSE RESISTANCE
(6b)
FIGURE 6. Measurement of Diode Resistance.
0172

OPERATING INSTRUCTIONS MODEL 167
3-7. OPERATION AS AN AMMETER. When the Model 167 is used with the optional
accessory Model 1673 Current Shunt, the Model 167 can be used to measure up
to 2 amperes. To measure current set the Shunt Resistor to 1 ohm and connect
the source in series with the 1673 terminals as shown in Figure 7. Install
probe in front panel, select either "ACV" or "DCV" FUNCTION and observe read
ing on the display. Increase the Shunt Resistor until the maximum display
is achieved not exceeding 2 volts. The current should then be calculated
from the following formula: Current = Voltage / Shunt Resistance.
CAUTION
If the voltage across the shunt exceeds 2 volts the accuracy may be de
graded and permanent damage may result.
NOTE
The accuracy for the Model 1673 Current Shunt is specified as H;0.3%.
The total inaccuracy when making a current measurement should include the
basic accuracy of the Shunt Resistor, the Model 167, and the loading ef
fects. The loading error in percent of reading can be calculated when the
source resistance is known. The % error is equal to 100R,/(Rs + R)
V. lere R = Shunt Resistance, Rs = Source Resistance.
SHUNT INPUT
TERMINALS
1^
VOLTAGE
DISPLAY
SELECTOR
SWITCH
FIGURE 7. Operation As An Ammeter
10
0172

MODEL 167
OPERATING INSTRUCTIONS
■■i
AC
■. I O Q Q DC
k a
M8
OVERRANGE
FUNCTION
7.'3S3
AC
DC
kO.
Mft
LIGHTED BAR
DECIMAL POINT
POLARITY
FIGURE 8. Digital Display
The digital display indicates three digits plus an over-
range
decimal location, polarity, and function. A
lighted bar identifies the function selected. When "DCV"
is selected, the polarity for negative inputs is indicated
by a "minus" sign. A positive polarity is not indicated,
but a positive input is implied when the "minus" sign is
turned off.
0172
11

OPERATING INSTRUCTIONS MODEL 167
3-8. BATTERY OPERATION. The Model 167 is shipped from the factory with six
alkaline "D" cells installed in the battery compartment so that the Model 167
is ready-to-use,
a. Battery Types Used in Model 167. The Model 167 operates from either of
two types of batteries listed in Table 3-1. The alkaline cells are non-re-
chargeable and should be replaced when batteries are worn out. The nickel-
cadmium cells are rechargeable when used with the optional Model 1671 Recharger.
b. Battery Test. To test the battery voltage while the Model 167 is op
erating, depress the "DCV" pushbutton and touch the probe to the "BATTERY TEST"
terminal on the rear panel. Depress the "push-to-read" bar along the top of
the probe and read the voltage displayed on the probe. Replace the alkaline
cells if the voltage is less than 6 volts. If nickel-cadmium cells are in
stalled, recharge using the Model 1671 Recharger if the voltage is less than
7 volts. The battery voltage should be at least 7 volts under load to ensure
that the instrument will turn on.
NOTE
The 167 contains an automatic shut-down feature which turns off the instru
ment if the power input voltage is too low or a fault occurs inside the
instrument.
c. Battery Replacement. The battery compartment is accessible from the
underside of the Model 167 chassis. Remove the battery cover (Item 3) by un
screwing the three slotted screws (Item 5) as shown in Figure 9. Grasp the
battery cover using the opening as a handle and gently lift the cover while
pulling toward the front panel to release the tabs. Remove the worn out bat
teries. Replace with new batteries as recommended in Table 3-1. When install
ing batteries, observe the polarity marked in the battery compartment. Replace
the battery cover by aligning the four tabs to mate with the four slots on the
chassis toward the rear panel. Make certain the tabs are fully engaged so that
the 3 screw holes align properly. Replace the 3 screws to complete the reassem
bly.
d. Battery Charging. To recharge the nickel-cadmium cells, connect the cable
from the Model 1671 Recharger to the "AUXILIARY POWER" receptacle on the Model
167 rear panel. Set the "Line" switch on the Model 1671 to "117V" for voltages
over the range of 90 to 125V rms or to "234V" for voltages over the range of
180 to 250V rms. Connect the line cord on the Model 1671 to a 50-60 Hz line
voltage. The Model 1671 Recharger automatically charges the Model 167 whenever
line voltage is connected. The charging rate is sufficient to completely re
charge a set of nickel-cadmium cells within 16 hours. Since overcharging will
not affect the batteries or the Recharger, the Model 167 can be recharged un
attended without any problem. The Model 167 may be operated while the recharger
is connected although the charging time will be longer.
CAUTION
Do not charge alkaline, zinc-carbon, or mercury batteries since the cells
may leak or explode causing subsequent damage to the instrument.
12 0172

MODEL 167
OPERATING INSTRUCTIONS
§
FIGURE 9. Battery Installation
0172
13

OPERATING INSTRUCTIONS MODEL 167
3-9. LINE OPERATION. The Model 167 can be powered from line power when used
with the optional Model 1672 Line Adapter. To operate from line power, connect
the cable from the Model 1672 Line Adapter to the "AUXILIARY POWER" receptacle
on the Model 167 rear panel. Set the "Line" switch on the Model 1672 to "II7V"
for voltages over the range of 90 to I25V rms or to "234V" for voltages over
the range of 180 to 250V rms. Connect the line cord on the Model 1672 to a
50-60 Hz line voltage. The Model 1672 automatically powers the Model 167 when
ever line voltage is connected. When batteries are installed the Model 1672
automatically switches to line operation as soon as the line cord is connected
so that battery power is not used. If a line voltage failure occurs or the
Model 1672 is disconnected, the Model 167 automatically switches to battery
operation. If no batteries are installed, set the instrument to "OFF" before
the line adapter is connected to ensure proper turn-on.
3-10. AUXILIARY POWER OPERATION. The Model 167 can be powered from an auxil
iary power source supplying +7 to +15 volts dc at 2 watts. Connections should
be made using the optional Model 1677 Power Cable which mates with the "AUXIL
IARY POWER" receptacle on the rear panel of the Model 167.
NOTE
The Model 167 has an automatic circuit that switches from battery oper
ation to auxiliary power whenever an auxiliary voltage is applied which
is greater than the battery test voltage. If the auxiliary voltage is re
moved or is less than the battery voltage, the Model 167 automatically
switches to battery power. If no batteries are installed, set the instru
ment to "OFF" before the auxiliary power is applied to ensure proper
turn-on.
3-11. BATTERY LIFE. The expected battery life is determined by usage per day,
ambient temperature, and charge time (for Ni-Cad rechargeable batteries only).
a. Non-rechargeable Type (Alkaline). The useful battery life for this type
will depend on the ambient temperature and the frequency of use. Alkaline bat
teries are recommended for up to 20 hours of continuous operation. When the
"push-to-read" switch is used intermittently, the 167 operates for a much
longer time. Since alkaline cells give maximum efficiency under intermittent
drain, the actual useful life can be as great as 25,000 measurements (assuming
about 3 seconds time per measurement). Battery life is reduced when operated
at temperatures below 70°F although the instrument will operate down to 32°F.
b. Rechargeable Nickel-Cadmium Cells. The useful battery life for this type
will depend on the temperature, frequency of use, and frequency and time of re
charging prior to use. Ni-Cad cells are recommended for up to 12 hours con
tinuous operation. Since the 167 utilizes a "push-to-read" bar, power is drawn
from the batteries only when the bar is depressed to turn-on the instrument.
Ni-Cad cells lose approximately 1% of potential per day when not used; there
fore, recharging should be accomplished at least once per week to ensure ad
equate battery voltage. When using the Keithley accessory Model 1671, Ni-Cad
cells should be recharged at least 16 hours to ensure a full charge. Over
charging will not harm the cells or the Recharger.
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