12227 Simpson, 12227 Datasheet - Page 14

• Manufacturer Part Number: 12227
• Description: Analog Multimeters 270-5RT VOM HI A
• Manufacturer: Simpson

Specifications of 12227

• Accuracy: +/- 1.75 %
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.2
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m. Remain alert for low voltage circuits which may be floating at high voltage
n.
o.
The function switch provides a convenient means to reverse polarity of the inter-
nal battery to facilitate testing semiconductor devices. The +DC and -DC posi-
tions transpose internal connections to the COMMON and + jacks and therefore
can also be used to reverse polarity of external voltages and currents connected
to these jacks (only). Because polarity reversing momentarily interrupts the cir-
cuit, it should not be done while measuring current without first turning off the
The 270 should only be used by personnel qualified to recognize shock
hazards and who are trained in the safety precautions required to avoid
possible injury.
Do not connect any terminal of this Instrument to a circuit point at which a
voltage exceeding 1000 volts AC or DC may exist with respect to earth
ground. (Refer to Table 1-1, item 16.)
Turn off power and discharge any capacitors in the circuit to be measured
before connecting to or disconnecting from the circuit.
Before using this Instrument, check accessories (if any) and test leads for
missing, damaged, deteriorated or otherwise faulty insulating parts. Do not
use, or permit the use of, equipment with faulty insulation until it has been
properly repaired.
Always wear safety glasses when working in electrical circuitry.
Do not work alone on high voltage circuits. Make certain that someone
capable of giving aid is nearby and alert to potential problems.
Do not handle the instrument, test leads, or circuitry while high voltage is
being applied.
Hands, shoes, floor, and workbench must be dry. Avoid measuring under
humid, damp, or other environmental conditions that could affect the dielec-
tric withstanding voltage of the test leads or Instrument.
Do not change switch settings or test lead connections while the circuit is
energized. A mistake could damage the Instrument or cause personal injury.
Locate all voltage sources and accessible current paths before making con-
nections to circuitry. Voltage may appear unexpectedly or in unexpected
locations in faulty equipment. An open bleeder resistor, for example, may
result in a capacitor retaining a dangerous charge.
Make certain that the equipment being worked on is properly grounded and
fuses are of the proper type and rating.
Double check switch positions and jack connections before applying power
to the Instrument.
with respect to earth ground and for composite voltages (AC + DC) such as
are found in r-f amplifiers. The floating voltage or composite voltage must not
exceed the Instrument’s rated maximum circuit-to-ground voltage.
Do not measure where the air may contain explosive concentrations of gas
or dust such as in mines, grain elevators, gasoline stations or in the pres-
ence of charging batteries until determined to be safe by qualified personnel.
Note that even metallic dusts can be explosive.
No general purpose VOM is to be used to make electrical measurements on
blasting circuits or blasting caps. Use VOMs designed for this purpose only.
Polarity Reversing
14
!
4.11
Turn off power to the circuit and wait until the meter indicates zero before discon-
necting the test leads.
Measuring the AC component of an Output Voltage where both AC and DC volt-
age levels exist is sometimes necessary. This occurs primarily in amplifier cir-
cuits. The 270 has a 0.1 mfd, 400 volt capacitor in series with the OUTPUT jack.
The capacitor blocks the DC component of the current in the test circuit, but
allows the AC or desired component to pass on to the indicating instrument
circuit. The blocking capacitor may alter the AC response at low frequencies but
is usually ignored at audio frequencies (Figure 4-4).
Do not connect the OUTPUT jack to a circuit in which the DC voltage component
exceeds 350V.
Before proceeding with the following steps, review the Safety Precautions in
Paragraph 4.1.
a.
b.
c.
Output Voltage Measurement
Set the function switch at AC (Figure 4-5).
Plug the black test lead into the - COMMON jack and the red test lead into the
OUTPUT jack.
Set the range switch at one of the range positions marked 2.5V, 10V, 50V, or
250V.
Figure 4-4. Frequency Response Output Ranges
+10
+8
+6
+4
+2
-2
-4
-6
-8
-10
0
10Hz
250 VAC RANGE
2.5 VAC RANGE
50 VAC RANGE
OUTPUT RANGES
10VAC RANGE
100Hz
1KHz
!
FREQUENCY
19
10KHz
100KHz
1MHz