Enter And Store; High Resolution Mode - HP 3455A Operating And Service Manual

Section Il
This leaves two equations to solve for the unknown ''y"'
and ''z"' constants. The two constants can be found the
following way:
-200,000 (y) _ Lower Limit - z
+ 200,000 (y) = Upper Limit - z
0 = Lower Limit + Upper Limit -2Z
(add these two equations)
therefore, z = Upper Limit + Lower Limit
2
200,000 = Upper Limit - z
y
200,000 (y) = 8 nee
Upper Limit - Upper Limit + Lower Limit
2
= Upper Limit - Lower Limit
2
and y Upper Limit - Lower Limit
400,000 -
The following is an example of how to use this math
technique. In this example a DC voltage is measured
and compared with a Lower Limit of 10 volts and an
Upper Limit of 30 volts:
30 - 10
y= Upper Limit - Lower = ,00005
400,000 400,000
z = Upper Limit + Lower Limit _ 30 + 10 = 29
2 2
By entering .00005 into the ''y'' register and 20 into the
"2" register, and then pushing the SCALE and DCV
buttons, the 3455A becomes a limit testing DVM. If the
input exceeds 30 volts a ''+ LL'? is displayed, and if the
input is less than 10 volts a ''-LL"' is displayed. If the in-
put is within the limits set, a number is displayed.
3-22. % Error Mode. The % error mode of the math
feature is described by the formula:
result in: % = _X-¥Y * 100
y
where is the present measurement value and ''y'' is
the reference value. An application of this feature might
be an inspection test of resistors. This nominal resistor
value would be entered in the ''y"' register in kilohm
(3455A) resistance measurements are presented in
kilohm). As an example, assume the test is made on a
group of 750 ohm resistors with a tolerance of 5%. The
nominal resistor value (750 ohms) is entered in the 'ty''
register as .750. The % error equation becomes: result
in % = X-.750 x 100. A resistor with
750
an actual value of 790 ohms would give a measurement
result of: % error = -790-750 x 100 = 5.33333%,
750
indicating the resistor is out of tolerance by .33333%.
ey
3-4 RevA
Modet 3455A
3-23. Enter and Store.
3-24, The ''Y'' and '*Z'' ENTER keys have two func-
tions. When one of the enter keys is pressed, the number
presently stored in the respective memory register is
displayed on the front panel readout. This allows the
operator to check the contents of the ''Y'' or ''Z''
memory registers. Pressing the enter key also ''shifts''
the front panel keyboard, disabling all keys except-those
labeled in blue. These keys can now be used to enter the
desired values to be stored in the ''Y"' or ''Z''? memory
registers. As the value is entered it is displayed on the
front panel readout. Numerical values from .000000 to
+ or - 199,999,9 may be entered in either the Y or Z
registers.
3-25. The STORE keys are used to transfer the number
presently being displayed in the ''Y'' or ''Z'? memory
registers and to return the voltmeter to normal opera-
tion.
3-26. The following describey how the ENTER and
STORE features may be used:
a. To view the value presently in memory, press the
ENTER key of the appropriate register (ENTER Y or
ENTER Z). To return this number to memory, press the
STORE key of the appropriate register.
b. To enter a new number, press the ENTER key of
the register to receive the number. Enter the desired
number into the display by pressing the keys labeled in
blue. Store the number entered by pressing the STORE
key of the appropriate register.
c. To enter a measurement value presently being
displayed, press the STORE key of the desired register
(¥ or Z).
NOTE
The operation of the ENTER and STORE
keys are not mutually exclusive. That is, the
number being displayed may be stored in
either the Y or Z register independently of
the register selected by the ENTER keys.
3-27. High Resolution Mode.
3-28. When the 3455A is used in the HIGH RESOLU-
TION mode, the instrument changes from a 5-1/2 digit
measurement to a 6-1/2 digit measurement. This
changes the measurement resolution from 10 parts/1.5
million (5-1/2 digit mode) to 1 part/1.5 million (6-1/2
digit mode). The integration period will also change
from 1/60 second (1/50 second for 50 Hz operation) to
8/60 second (8/50 second for 50 Hz operation). The
High Resolution mode cannot be used in the AC mode
or the .1 V DC and | K ohm ranges. The reading rate in
the DC and Ohms mode will also increase when the
High Resolution function is turned off. Table 3-1 gives
the various reading rates of the DC and Ohms functions