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MODEL 252 Digital Impedance Meter Instruction Manual P/N 43158-CD Rev F This owner’s manual was as current as possible when this product was manufactured. However, products are constantly being updated and improved. Because of this, some differences may occur between the description in this manual and the product you received.
TABLE OF CONTENTS DANGEROUS VOLTAGE POTENTIALS EXIST INSIDE THIS INSTRUMENT. MAINTENANCE INSTRUCTIONS WITHIN THIS MANUAL ARE FOR USE BY QUALIFIED SERVICE PERSONNEL ONLY. TO AVOID ELECTRICAL SHOCK, DO NOT ATTEMPT ANY SERVICING OTHER THAN THAT CONTAINED IN THE OPERATION INSTRUCTIONS UNLESS YOU ARE QUALIFIED TO DO SO. 1 DESCRIPTION 1.1 INTRODUCTION 1.2 SPECIFICATIONS...
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TABLE OF CONTENTS (continued) 4 MAINTENANCE 4.1 CALIBRATION PROCEDURE 4.1.1 Power Supply Check 4.1.2 Oscillator Adjust 4.1.3 L, C, R, G Alignment 4.1.4 Dissipation Factor (D) Alignment 4.2 MAINTENANCE 4.2.1 Preventive Maintenance 4.2.1.1 Cleaning 4.2.1.2 Visual Inspection 4.3 PREPARATION FOR CALIBRATION OR REPAIR SERVICE 4.4 WARRANTY...
3-1/2 digit LED readout. Excellent reliability of the Model 252 is assured through use of solid-state devices and etched circuit board construction. Its small size is ideal for use on bench tops where work space may be at a premium.
1.2 SPECIFICATIONS Table 1-1. Model 252 Specifications Test Frequency: 1kHz ±1%. Unknown Excitation: The 1kHz voltage (Vx) and current (Ix) levels listed in Table 1-1 are held constant by an internal amplitude control circuit. Measurement Rate: Four per second; one second is required for first reading after connecting unknown to terminals.
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Connection to Unknown: Four-terminal, shielded, connections are provided by the KELVIN KLIPS® cable assembly (Tegam Part Number 43072) supplied with the Model 252. Outputs: Analog signals of 1V per 1,000 counts, 1kΩ source resistance is available at rear panel. L, C, R, or G, with simultaneous output of D for L or C.
2. UNKNOWN Connector – Terminals designed to be used with KELVIN KLIPS® test leads (Tegam Part No. 43072), Provided with Model 252, to provide a true Four-terminal connection to the unknown or Test fixture. 3. L, R, C, and G Pushbuttons – Function pushbuttons select the type...
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4. D Pushbutton The push-to-read D (dissipation factor) pushbutton displays the D of a capacitor or inductor when the C or L function is selected. 5. Range Switch Selects the decimal multiplier and units of measurement for the meter circuit being used.
DVM’s (for increased full scale readings or resolution capability), with chart recorders, or with limits comparators, such as the Tegam Model 1412B. Fuse – A 1/16A, 250V, type MDL Slow Blow for 110V line voltage, or a 1/20A, 250V...
Before turning the power ON, make sure the instrument is set to the proper line voltage. The Model 252 contains an internal slide switch to select the nominal line voltage (see Figure 2-3). In its up position, the switch selects 100 to 125VAC, 50/60Hz operation. In the down position it selects 200 to 250VAC, 50/60Hz operation.
Because of differing power requirements, all instruments shipped outside the United States are without a power cord connector. When placing a connector on the power cord, care must be taken to assure the wires are connected properly. The green or green with yellow stripe wire is always connected to earth ground.
2.2.3 Connection to Unknowns The KELVIN KLIP® test lead set (Tegam Part No. 43072) is plugged into the 252’s front panel UNKNOWN connector. The test leads connector cover is spring-locking and should be squeezed together before inserting or removing. The test leads provide a shielded, four-terminal connection to the unknown (see Figure 2-5a). The clip with the red hinge-spool provides the HI DRIVE and HI SENSE connections to the unknown and the clip with the black hinge-spool make the LO DRIVE and LO SENSE connections.
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Figure 2-5b. For connection to three terminal unknowns (the third connection is to ground), a ground wire must be added to the test lead set. This wire is connected as in Figure 2-5b.
The Model 252 uses a 3.3pF capacitor (C6 in Figure 2-6) to compensate for the capacitance of the test leads. If the 252 is used with a test fixture, the larger capacitance of the fixture must also be compensated for. There are two methods for compensating this larger capacitance. The first method is to make a zero capacitance measurement with the test fixture connected.
2.2.4 Function Selection Model 252 is designed to measure series inductance (L), parallel capacitance (C), series resistance (R), parallel conductance (G), and dissipation factor (D) of inductance and capacitance. One of these measurement modes is selected by depressing the proper front panel button. (If all buttons are in their out position, the instrument reverts to the inductance measurement mode.)
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Example: Select the conductance measurement function. (Depress the G Pushbutton.) If a negative sign appears on the display when measuring an unknown, possible causes are: “C” button has been pushed when measuring an inductor. “L” button has been pushed when measuring a capacitor. The unknown is more capacitive (or inductive) than suspected.
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(R or G). In moving to the next lower range, the reactive component becomes too large for the lower range causing overload and a blanked display. Example: while measuring a 0.82µF capacitor using the 2µF range, the 252 display reads: Switching to the conductance (G) mode, the display may read:...
Trying further to investigate this reading, you down range from the 20mS range to the 2000µS range. The display blanks: The display blanks because, while ranging from 20mS to 2000µS, the capacitance range changed from 2µF to 200nF. Since 0.82µF is too large to measure on the 200nF range, an overload occurs and the display blanks.
Example: Set the instrument to measure 100pF capacitors. Example: Set the instrument to measure 100kΩ resistors. If the value of a component is not known, set the instrument to its highest range before connecting the test leads. Step the instrument down one range at a time until the range with the highest resolution is reached.
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unknown exceeds the range selected, the display will remain blanked. To measure the dissipation factor of a capacitor or inductor, push and hold the D button while the C or L function is selected. 2-14...
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Equivalent Series Resistance (ESR). To measure series resistance of capacitors, use the Rs function. Series resistance will be displayed on the front panel. Series Capacitance. The Ls function can be used to measure series capacitance. (The capacitor is measured with a constant current rather than a constant voltage.) A negative reading will be shown, and the following equation must be used to convert the “-L ”...
Cp and D values of the capacitor. To locate the Cs value, find the measured D value along the horizontal axis of the graph. (The D reading from the Model 252 will be a Dissipation Factor value not a Percent Dissipation value.) Move up the graph to the B curve and read...
2.3.3 Inductance Measurements The 252 measures the total impedance connected to its terminals. Both the unknown inductor and it’s leads contribute to this impedance. The leads have some resistance and inductance which affect the value read from the meter. In making high inductance measurements, avoid AC pickup and keep the stray capacitance to a minimum.
2.3.5 Determining Dissipation Factor (D) of Capacitors Using Nomograph Model 252 will measure dissipation factor up to 1.999. For D values greater than 2 the nomograph should be used. Measure the capacitance of the unknown and record the readout display in digits only; do not record the decimal point. With the RANGE switch left in the same position, push the G button and note the readout display in digits only;...
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Figure 2-8. Model 252 D-Q Nomograph 2-21...
2.3.6 Using the Bias Feature TO AVOID PERSONAL INJURY FROM ELECTRICAL SHOCK OBSERVE SAFETY PROCEDURES AS NEEDED FOR THE BIAS VOLTAGE APPLIED. Bias voltage is necessary or desirable when measuring the capacitance of diodes or of some electrolytic or tantalum capacitors. There is a provision on the rear panel for connecting an external bias source of zero to 50VDC.
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3. Locate the Power Supply Circuit Assembly, Part No. 53157. (Attached to the rear panel.) 4. Remove jumper wire W1 from this assembly (see Figure 2-10). Figure 2-10. Power Supply Circuit Assembly 5. Locate the Range Switch on the front panel. 6.
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The modification of instruments with Serial Numbers 929000 and greater is as follows: 1. Locate the connector strip on the rear panel (see Figure 2-12). 2. Remove and isolate the spade lug from the terminal marked COM. Figure 2-12 To make measurements of grounded unknowns, connect the grounded side of the unknown to the KELVIN KLIPS®...
5. Move the range switch to the range with the highest resolution displayed (see Section 2.2.5) unless that range uses excessive test current for the size of battery being measured. See Table 1-1 for range test currents. Figure 2-14. Measuring Battery Impedance 2-27...
Cs = series capacitance in farads Ls = series inductance in henrys Care must be taken so the measurement current level of the 252’s internal source does not exceed the rating of the battery being tested. See Table 1-1 for range test currents.
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LO indicates value less than - % limit. HI indicates value greater than +% limit. D HI indicates dissipation factor greater than limit. Connect the 252 and 1412B as shown in Figure 2-15. Tegam Part No. 42855 Figure 2-15 Model 252 and Model 1412B Interconnection...
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Set LIMITS FULL SCALE toggle switches, and % LIMITS and D LIMIT dials to desired limits. The measurement: Connect unknown to the Model 252. If the unknown is within the set limits, the GO LED will light. If it is not within limits, the appropriate indicator will light. 2-30...
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Example: Sort 15 µF capacitors within +25%, -15% limits with a maximum dissipation limit of 0.0250. Instrument set up is as follows: Model 252: Function and Range settings 2-31...
SECTION 3 CIRCUIT DESCRIPTIONS GENERAL DESCRIPTION When measuring Cp or Gp, a voltage is applied across the unknown and range resistor in Figure 3-1. The voltage across the unknown is held constant to within one part in several thousand by the 1kHz oscillator feedback control circuit. A current proportional to the value of the unknown impedance is produced through the range resistor.
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(Ls or Cp) and presents a voltage proportional to D to the A/D Converter. Analog output voltages are available at the rear of Model 252 for the selected function (L, C, R or G) and simultaneous D (for L or C unknowns).
4.1.1 Power Supply Check Setup – turn on instrument and allow ten minute warm-up period; then remove cover. Check – Power supply voltages at C44 and C45 should be + and -5V +/-5% (4.75V to 5.25V). Use rear panel COM terminal for voltmeter low input. 4.1.2 Oscillator Adjust Setup –...
4.1.4 Dissipation Factor (D) Alignment 1. LOW LEVEL ZERO TRIM. Setup – Press C function button and set RANGE switch to 200nF. Connect a low loss (D<0.0002) decade capacitor to unknown test leads. Adjustment – Set the decade capacitor to 105nF and, with a DVM, note the voltage at J5 pin (3) or D output terminal at the rear panel.
4.2 MAINTENANCE This section of the manual contains maintenance information for use in preventative maintenance, corrective maintenance,and troubleshooting of the Model 252. 4.2.1 Preventative Maintenance REMOVAL OF INSTRUMENT COVERS MAY CONSTITUTE AN ELECTRICAL HAZARD AND SHOULD BE ACCOMPLISHED BY QUALIFIED SERVICE PERSONNEL ONLY.
TEGAM for service. Before sending a unit in for service, an RMA, (Returned Material Authorization), number must be assigned to your instrument. You can contact TEGAM customer service via the TEGAM website, www.tegam.com...
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Expedite Repair & Calibration Form Use this form to provide additional repair information and service instructions. The Completion of this form and including it with your instrument will expedite the processing and repair process. RMA#: Instrument Model #: Serial Company: Number: Technical Contact: Phone Number:...
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The foregoing warranty of Tegam is in lieu of all other warranties, expressed or implied. Tegam specifically disclaims any implied warranties of merchantability or fitness for a particular purpose. In no event will Tegam be liable for special or consequential damages. Purchaser’s sole and exclusive remedy in the event any item...
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