HP 3478A Technical Manual page 37

3478A 3478A
lions, listed in Table 1-1 and Table 4-1 lions, listed in Table 1-1 and
performance standards or limits against which the 3478A performance standards or limits against which the 3478A
can be tested. Table 1-1 can be tested. Table 1-1 also
characteristics of the 3478A and should be considered characteristics of the 3478A and should be considered
as additional information. as additional information.
4-34. 4-34. Any changes Any changes in in the
manufacturing changes, design, or traceability to the manufacturing changes, design, or traceability to the
National Bureau of Standards will be covered in a National Bureau of Standards will be covered in a
manual change manual change supplement supplement or or revised
specifications listed here supercede any previously specifications listed here supercede any previously
published. published.
4-35. Specification 4-35. Specification Breakdown Breakdown
4-36. The 3478A's specificat 4-36. The 3478A's specifications are grouped
to instrument function (AC Volts, DC Volts, etc.). Within to instrument function (AC Volts, DC Volts, etc.). Within
each group are either one, two, or three main sets of each group are either one, two, or three main sets of
specifications: the 24 hour, 90 day, and 1 year limits. specifications: the 24 hour, 90 day, and 1 year limits.
The limits to which the 3478A conforms depends on The limits to which the 3478A conforms depends on
when the instrument was last calibrated or to which it when the instrument was last calibrated or to which it
was certified, and the was certified, and the instrument function. instrument function. The 24 hour
limits should only be used if the instrument was limits should only be used if the instrument was
calibrated within the last 24 hours, otherwise, the 90 day calibrated within the last 24 hours, otherwise, the 90 day
or 1 year limits apply. or 1 year limits apply.
4-37. Each set 4-37. Each set of specifications of specifications includes an
specification for each voltage, ohms, and current range. specification for each voltage, ohms, and current range.
They are specified as a percentage of the reading and They are specified as a percentage of the reading and
an add-on o an add-on of a certain f a certain number of counts.
the 24 hour full scale DC Volts Function accuracy on the the 24 hour full scale DC Volts Function accuracy on the
30V Range (in the 5 Digit 30V Range (in the 5 Digit Display Mode) is:
.005% of reading + 3 counts .005% of reading + 3 counts
± ±
giving a full scale accuracy of +.005% or (5 counts) plus giving a full scale accuracy of +.005% or (5 counts) plus
3 counts (or .003%0), which is a total of 8 counts (or + 3 counts (or .003%0), which is a total of 8 counts (or +
.008%). .008%). (This is only (This is only true at fu true at full scale and chan
1/10 scale, see next paragraph.) If for example the 4 1/10 scale, see next paragraph.) If for example the 4
Digit Display Mode is selected, the percentage is the Digit Display Mode is selected, the percentage is the
same (.005%o), but the number of counts is different and same (.005%o), but the number of counts is
changes the total percentage to + .015% (.005% plus 1 changes the total percentage to + .015% (.005% plus 1
count in the 4 Digit Mode is count in the 4 Digit Mode is .01%o which makes the total
equal .015%). equal .015%).
4-38. The number of 4-38. The number of counts also cha counts also changes the accura
of the 3478A at 1/10 scale. of the 3478A a t 1/10 scale. For example, the percenta
(same Function, Range, and Digit Mode) at 1/10 scale is (same Function, Range, and Digit Mode) at 1/10 scale is
still .005 still .005%o at %o at 1/10 scale. 1/10 scale.
counts (3) is .03% at 1 counts (3) is .03% at 1/10 scale.
.035%, rather than .008% at full scale. .035%, rather than .008% at full scale.
4-39. 4-39. Temperature Temperature
Temperature) Temperature)
4-40. 4-40. The temperatu The temperature in re in which th
calibrated is is called calibrated called its its Reference
maintain the 3478A's specified accuracy, the multimeter maintain the 3478A's specified accuracy, the multimeter
must be operated within the specified range of that must be operated within the specified range of that
temperature (shown in Table 1-1 temperature (shown in Table 1-1). ). If the
or operated outside the temperature range, the or operated outside the temperature range, the
Table 4-1, are the
also lists lists some some supplemental supplemental
the specifications specifications due
revised manual. manual.
ions are grouped according
The 24 hour
includes an accuracy
number of counts. For example, For example,
Display Mode) is:
ll scale and changes at
different and
.01%o which makes the total
nges the accuracy cy
For example, the percentage
However, However, the number the number of of
/10 scale. This gives a total of This gives a total of
Coefficient Coefficient (Reference (Reference
which the 3478A e 3478A was last
Reference Temperature. Temperature.
If the 3478A is 3478A is tested
, are the Temperature Coefficient (listed in Table 1-1) Temperature Coefficient (listed in
added added
recommended to calibrate the 3478A in the temperature recommended to calibrate the 3478A in the temperature
in which it is to in which it is to be tested and operated.
4-41. TEST 4-41.
4-42. General 4-42. General
due to to
4-43. 4-43.
The The accurate dc measurements, certain requirements have accurate dc measurements, certain requirements have
to be met. For example, the Digital Voltmeter that is used to be met. For example, the Digital Voltmeter that is
to test and calibrate the 3478A should be good enough to test and calibrate the 3478A should be good enough
so that its errors do not introduce any significant so that its errors do not introduce any significant
uncertainties in the Performance Test a uncertainties in
voltmeter which is 10 times better than the 3478A nearly voltmeter which is 10 times better than the 3478A nearly
according eliminates the uncertainties. eliminates the
standards) with these accuracies are not readily standards) with these accuracies are not readily
available, use the recommended Digital Voltmeter. Make available, use the recommended Digital Voltmeter. Make
sure the voltmeter has been calibrated to its 24 hour sure the voltmeter has been calibrated to its 24 hour
specifications and used within 24 hours after calibration, specifications and used within 24 hours after calibration,
before testing and calibrating the 3478A. before testing and calibrating the 3478A.
4-44. 4-44. Ambiguous
4-45. 4-45. Since the av
of magnitude better than the 3478A, it is important to be of magnitude better than the 3478A, it is important to be
aware of the uncerta aware of
accuracy
is in the next paragraph. is in the next paragraph.
4-46. A hypothet 4-46.
scale dc accuracy with a certain scale dc accuracy
90 day specification is -.01% with the standard's 90 day specification is -.01% with the standard's
accuracy accuracy ideally
reading is "30.0033" (.011% high), the multimeter may or reading is "30.0033" (.011% high), the multimeter may or
may not meet its 90 day limit (dependent on the may not meet its 90 day limit (dependent on the
standard's standard's accuracy).
(30.0003V), the 3478A's actual reading is "30.0030" (30.0003V), the 3478A's actual reading is "30.0030"
ges at which is in the 90 day which is in th
on, the 3478A reading is "30.0033" (its reading is high on, the 3478A reading is "30.0033" (its reading is high
and out of tolerance) and out
standard is within its limits, it may show the 3478A to be standard is within its limits, it may show the 3478A to be
in or out of its limits. in or out of
shown in Figure 4-1. shown in
3478A 3478A
specifications are specifications are less accurate.
you know your standard's actual limits. you know your standard's actual limits.
ge
was last
To To
tested
4-4 4-4
to to the the instrument's instrument's specifications.
be tested and operated.
TEST CONSIDERATION CONSIDERATION
Because the Because the 3478A 3478A is able
the Performance Test and Calibration.
uncertainties. Since voltmet
Ambiguous Region Region
Since the available test eq ailable test equipment is not
the uncertainties or "ambiguities". inties or "ambiguities". An example
A hypothetical case is to check the 3478A' ical case is to check the 3478A's 3V full
with a certain standard.
ideally .001% .001% (ten (ten times
accuracy). If the If the standard
e 90 day limit. limit. If the standard ou If the standard output is right
of tolerance). . Although in Although in both insta
its limits. This creates an Ambiguous Region This creates an Ambiguous Region, ,
Figure 4-1. The region gets bigger when the The region gets bigger when the
limits limits are are tighter tighter
less accurate. The best t
Figure Figure 4-1. 4-1. Ambiguous Ambiguous Regions
TM 11-6625-3071-14 TM 11-6625-3071-14
Table 1-1) must be must be
specifications. It It
is able to to make highly make highly
used
nd Calibration. A A
Since voltmeters (or e ers (or even ven
uipment is not an order an order
An example
s 3V full
standard. The 3478A's The 3478A's
times better). better). If If the the 3478A 3478A
standard is .001% is .001% high high
tput is right
both instances the nces the
and/or and/or the the standard's standard's
The best test is when est is when
Regions
is is