HP TM 11-6625-2779-14&P Noise-to-Ground Measurements Balance Measurement, Recorder Calibration

Section III	Model 3555B
Table 3-5. Noise-to-Ground Measurements	Table 3-6. Balance Measurement

STEP PROCEDURE

1.Turn the 3555B POWER switch to ON and depress the DIAL/BAT pushbutton. The meter should indicate in the green BAT GOOD area. If it does not replace the battery or check the power source. The battery test operates for internal battery, office battery or ac power source.

2.Set the INPUT switch to NOISE BRDG.

3.Select the appropriate weighting filter using the NOISE WTG switch.

4.Set the RANGE switch to 110dBrn.

5.Depress the NG pushbutton and connect the set to the circuit to be tested. Down range for an on-scale indication.

NOTE

Dial and talk may be accomplished on the metallic circuit and the connection held by depressing the HOLD pushbutton.

Table 3-7. Recorder Calibration

STEP PROCEDURE

1.Determine the input impedance and full scale sensitivity of your recorder and refer to paragraph 3-41and Figure 3-4to determine if your recorder is suitable for use with this set. The dc voltage supplied by the DC MON 310 jack will drive a dc potentiometric recorder requiring 1V or a dc galvanometric recorder requiring 500uA.

2.Connect an input voltage to the set and adjust the RANGE switch until a near full-scale indication is observed on the meter.

3.Connect the recorder plug with the tip negative, to the DC MON jack and adjust the input level until the meter indicates 0dBm. Mark this point on the recorder paper which should be near full scale.

4.Decrease the input level to the set until the' meter indicates -1dBm. Mark this point on the recorder paper. Continue this procedure until every major dBm division on the meter has been calibrated on the recorder paper.

5.The actual level to the set as indicated on the recorder is equal to the algebraic sum of the RANGE setting and recorder indication.

STEP PROCEDURE

1.Perform the Noise-to-ground measurement as described in Table 3-5.

2.Perform the Noise Metallic measurements as described in Table 3-4.

3.Compute the line balance in dB using the results of the above checks.

Balance (dB) = Nm - NG

EXAMPLE:
Noise-to-ground	=	+26dBrn
Noise Metallic	=	(-)+90dBrn
Balance in dB	=	-64dBm

NOTE

The noise-to-ground measurement above includes the 40dB correction factor.

Table 3-8. Transmission Loss Measurement

STEP	PROCEDURE
1.	For a transmission loss measurement to be
	meaningful, it should first be determined if
	there are any extraneous signals present that
	will affect your measurement. To do this,
	connect the measuring set to the circuit and
	determine if interfering signals are present.
	Levels below 60dB can, in most cases, be
	ignored. A butt-in can be connected to the AC
	MON jacks to aid in determining the
	interfering source.
2.	Establish a connection like the ones shown in
	Figure 3-6.
3.	Adjust the oscillator output level for 0dBm.
	Measure the level at the receiving end and
	record this level.
4.	Insertion loss is equal to the difference
	between the sending level and the receiving
	level, ignoring any extraneous signals.
	EXAMPLE:
	Sending level	=	0dBm
	Receiving level =		(-)- 20dBm
	Insertion loss	=	20dB

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