Altai NH-55 User manual with schematics

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MULTITESTER 2,000 ohms/volt model ALTAI NH-55

ATTAL

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Description

With a lot of meter built into a small package, the ALTAI NH-55 features a high 2000 ohms/volt sensitivity on all DC and AC voltage ranges. Also included are a convenient 100 mA DC range and two essential ohmmeter ranges. Capacitors and inductors can be measured using proceedures detailed below. A mirror arc has been included to help-eliminate parallax errors from readings. Built in a modern high-impact case, the ALTAI NH-55 is a quality product in both perfor- mance and appearance.

SPECIFICATIONS

DC Voltage:	0 - 10, 50, 250, 1000 volts.
	2,000 ohms/volt.
AC Voltage: Decibel:	0 - 10, 50, 250, 1000 volts, 2,000 ohms/volt - 10 to + 22 dB. On 10 V AC range.
De current.	1 - 100 mA

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Ohmmeter; Power Supply: Size: Weight:

0 - 10 Kilohms, 0 - 1 Megohms. One 1.5-volt size "AA" cell for ohmmeter 3-5/8" × 2-3/8" × 1-1/8" 4 oz., (including battery)

CONTROLS AND JACKS

RANGE switch: Use to select factor to be measured and range.

02ADJUST control: Use to set pointer to 0 (extreme right of meter scales) on uppermost ohmmeter scale, when test leads are connected to each other in an OHMS setting of the RANGE switch. Mechanical adjust: Screw on meter movement to set pointer to zero:

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JACK: Plug-in connection for black, negative, test lead.

+ JACK : Plug-in connection for red, positive, test lead.

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Operating Procedure

preliminary adjustments

1. Check the mechanical adjust, screw setting as following:
- a. Place the ALTAI NH-55 tester flat on a bench.
- b. Set the RANGE switch to 10 DCV.
- c. Connect one test lead to the other.
- d. Note if the meter pointer indicates exactly 0 at the extreme left end of the black scales.
- e. If it does not read 0, turn the screw on the meter movement slowly until the proper 0 reading is realized.
2. Check the battery as follows:
- a. Connect one test lead to the other.
- b. Set the RANGE switch to OHMS X10.
- c. Turn the 0 $\Omega$ ADJ control until you find the position. where the meter pointer indicates the full scale 0 on the $\Omega$ scale. If this adjustment cannot be made, replacethe 1.5 volt size "AA" cell. (See MAINTENANCE)

OPERATING SUGGESTIONS.

1. Set the RANGE switch to the proper voltage or current range before making measurements. Never apply more voltage or current than the amount noted on the front panel in each

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switch position. When in doubt as to the voltage or current present in a circuit, start with the highest range in each case. If the voltage or current is of such magnitude as to be measurable on a lower range, select the lowest range switch position which will provide you with a reading without causing the meter pointer to deflect off scale.

2. Do not check resistance when voltage or current is present in the circuit.
3. Discharge a capacitor before measuring it.
4. Avoid placing the tester, in a place where severe vibration is encountered. Do not store it in extremely hot or humid locations.
5. Remove the battery before storing the tester for a long period of time. Also rotate the RANGE switch from time to time to clean the contacts.
6. To extend the life of the battery never leave the tester in an OHMS setting when you are not in the process of measuring resistance.
7. For all measurements, plug the black test lead into the jack. Plug the red test lead into the + jack.

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8. You can see a reflection of the meter pointer in the mirror arc. To avoid parallax errors in your readings, look straight down. onto the meter scale. You are doing this perfectly if the mirrorr image of the pointer is covered by the actual meter pointer, so that you do not see its reflection in the mirrorr arc.

DC VOLTAGE MEASUREMENTS

Select the required dc voltage range or use the procedure in "1" above under OPERATING SUGGESTIONS. Connect the test leads across the circuit whose voltage is to be measured. Observe polarity. Read dc voltage on the appropriate scale.

DC CURRENT MEASUREMENTS

Select the 100mA dc current range. Connect the test leads in series with the circuit to be measured. Observe polari y. Read dc current on the appropriate scale.

Should the ranges provided not be sufficient to measure current in your circuit, the DCV anges of your ALTAI NH-55 may be utilized. Meas ure the voltage across a resistor in the circuit through which the current flows. If this is not possible, add a small res stor in series with the circuit. The added resistor, if used,

FIGURE 1

so as not to upset the circuit. Measure the voltage across this resistor, then calculate the current using Ohm's Law. See the example in Figure 1. Here, it is assumed that 2 volts is across a 100ohm resistor. The current through the resistor is:

1 = - = - = 2 × 10 - 2 = 20mA

AC VOLTAGE MEASUREMENTS

Select the required red ACV range or use the procedure in "1" above under OPERATING SUGGESTIONS. Connect the test leads across the voltage to be measured. Leads may be connected in either direction. Read ac voltage on the appropriate scale. Use the special scale when set to IOV AC

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AC CURRENT MEASUREMENTS

AC current cannot be measured directly on this instrument. However, if you need an ac current measurement, add a small resistor in series with the circuit. Measure the ac voltage across this resistor, then calculate the current using Ohm's Law. See the procedure and example under DC CURRENT MEASUREMENTS.

RESISTANCE (OHMS) MEASUREMENTS

Set the RANGE switch to an OHMS range. Connect one test lead to the other and set the 02 ADJ. control for full scale deflection. Separate the test leads and connect them across the resistor to be measured. Read the resistance or the 2 scale. Use the appropriate multiplier as required for the different resistance ranges.

DB RATIO MEASUREMENTS

The ratio of two ac voltages can be expressed in terms of dB. A standard has been adopted which establishes one reference voltage as the 0 dB level. It is 0.774 volt rms. This assumes that 1 milliwatt is developed across an impedance of 600 ohms.

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When using the 10-volt ac range, read the red dB scale.

INDUCTANCE MEASUREMENTS

Wire the circuit shown in Fig. 2 using a power transformer and variable ac supply voltage. Connect a 20k ohms resistor across the test leads. (Note: The 20k ohms resistor is used across the test leads when measuring inductance and high capacitance. A 500k ohms resistor is used across the test leads when measuring low capacitance.) Any inductance between 4 and 2000 henrys can be measured.

NOTE: Adjust voltage with variac before measuring capacitance or inductance. Transformer voltage and shunt resistor requirements are discussed in the text. Do not change variac voltage after setting has been made.

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1. Set the RANGE switch to 10 ACV. Connect the test leads across the secondary of the transformer, as shown in Figure 2. Starting at zero volts, slowly increase the ac voltage until you read 10 volts.
2. Connect the unknown inductor (drawn as a rectangular box marked L OR C) as shown in Figure 3. Note the voltage on the 10-volt scale. Use TABLE 1 to determine the inductance in the circuit from the voltage read on the meter. You can interpolate between values if the actual voltage read on the meter is not indicated on the table.

Circuit to measure inductance or capacitance.

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TABLE L VOLTAGE TO INDUSTANCE CONVERSION (4 HENRYS TO 2000 HENRYS)

RMS VOLTS	INDUCTANCE(H)	RMS VOI TS	INDUCTANCE(H)
9.88	4	3.14	80
9.83	5	2.81	00
9.75	6	2.56	90
9.67	.7	2.16	100
9.57	8	1.86	120
9.47	9	1.63	140
9.35	10	1.45	100
7.99	20	1.45	180
6.63	30	1.31	200
5.52	40	0.66	300
4.67	50	0.64	400
4.04	60	0.53	500
3.52	70	0.27	1000 2000

HIGH CAPACITANCE MEASUREMENTS (.005 TO 1 MFD)

1. Connect the circuit shown in figure 2, using a 20k ohms resistor.
2. Set the RANGE switch to 10 ACV. Connect the test leads across the secondary of the transformer. Starting at zero volts, slowly increase the ac voltage until you read 10 volts.

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3. Connect the capacitor (drawn as a rectangular box marked L or C) as shown in Fugre 3. Note the voltage on the 10-volt scale. Use TABLE 2 to determine the capacitance in the circuit from the voltage read on the meter. You can interpolate between values if the actual voltage read from the meter is not indicated on the table.

LOW CAPACITANCE MEASUREMENTS (100 TO 50,000 PF)

1. Connect the circuit shown in Figure 2, using a 500,000 ohms resistor.
2. Set the RANGE switch to 250 ACV. Connect the test leads across the secondary of the transformer. Starting at zero volts, slowly increase the ac voltage until you read 250 volts.
3. Connect the capacitor (drawn as a rectangular box marked L OR C) as shown in Figure 3. Note the voltage on the 250-volt scale. Use TABLE 3 to determine the capacitance in the circuit from the voltage read on the meter. You can interpolate between values if the actual voltage read from the meter is not indicated on the table.

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TABLE 2. VOLTAGE TO CAPACITANCE CONVERSION (.005 MFD TO 1 MFD)

	(mfd)	RMS VOLTS	CAPACITANCE (mfd)
.19 32 .38 .73 1.11 1.49 1.85 2.21 2.55 2.87 3.20 3.52 4.12	.005 .009 .01 .02 .03 .04 .05 .06 .07 .08 .09 .1 .12	4.67 5.15 5.61 6.01 6.86 7.49 8.34 8.83 9.14 9.35 9.50 9.58 9.67	.14 .16 .18 .2 .25 .3 .4 .5 .6 .7 .8 .9

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1	ABLE J.	VOL TAGE	TO CAPACITANC	ECONVERSIO
	1.000	MED TO	03 MED) (100 PED	50.000 PHD1

RMS VOLTS	CAPACITANCE (pF)	RMS VOLTS	CAPACITANCE (pF)
1.75	100	59	2600
45	200	64	2800
4.75	300	68	3000
9.75	400	78	3500
11.8	500	88	4000
	600	97.5	4500
	700	106.	5000
18.1	800	112	5500
21	900	124	0000
21 1	1000	130	6500
23.3	1200	137	7000
17.7	1400	151
17	1600	161	9000
47	1800	172	10k
46.7	2000	221	20k
	2200	236	30k
55	2400	245	SOk

Maintenance

Test the battery as described above in PRELIMINARY ADJUSTMENTS. If the battery must be replaced, remove the screw in the rear cover of the case, and lift the back off the front section. Note the orientation of the AA cell in its compartment. Replace the battery. The positive (+) end should be at the end so indicated in the case. Be sure that the contacts at each end of the compartment make good contact with the metallic battery terminal at its positive end and the metallic portion of the battery case as its negative end. Carefully replace the back onto the front of the case. Retighten the screw Do not tighten excessively, or you will strip the threads in the case.

SCHEMATIC DIAGRAM

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