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Polar Instruments T1500A Operator's Manual

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Polar Instruments Ltd.
Garenne Park
T1500A
Rue de la Cache
St. Sampson
OPERATOR
Guernsey
Channel Islands
MANUAL
GY2 4AF
England
Fax: +44 (0)1481 52476
MAN 151-9510

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  • Page 1 Polar Instruments Ltd. Garenne Park T1500A Rue de la Cache St. Sampson OPERATOR Guernsey Channel Islands MANUAL GY2 4AF England Fax: +44 (0)1481 52476 MAN 151-9510...
  • Page 3 POLAR INSTRUMENTS LTD and not having been altered in any way or subject to misuse, negligence or damage, and not having been repaired or attempted to be repaired by any other than POLAR INSTRUMENTS LTD or its authorized distributors.

  • Page 4: Declarations

    T1500A OPERATOR MANUAL DECLARATIONS ELECTROMAGNETIC COMPATIBILITY European Community Directive Conformance Statement This product is in conformity with the protection requirements of EC Council Directive 89/336/EEC on the approximation of the laws of the Member States relating to electromagnetic compatibility. A declaration of conformity with the requirements of the Directive has been signed by...

  • Page 5: Safety

    SAFETY SAFETY WARNING The LIVE and NEUTRAL lines on this unit are BOTH fused. This unit contains no user-serviceable parts. When the unit is connected to its supply, the opening of covers or removal of panels is likely to expose dangerous voltages. To maintain operator safety, do not operate the unit unless the enclosure is complete and securely assembled.

  • Page 6: Power Supply

    Retain these instructions for later use. The T1500A is designed for use indoors in an electrical workshop environment at a stable work station comprising a bench or similar work surface.

  • Page 7: Environmental Operating Conditions

    SPECIFICATIONS Open Circuit Voltage Short Circuit Current ASA Test Ranges Junction 500µA Logic 150mA High Hi-Cap (1Hz fixed) 150mA Low-Cap (2kHz fixed) 20µA ASA Test Frequencies 95Hz Medium 500Hz High 2kHz Display Internal CRT Power Requirements 230V ± 10%, 115V ± 10% or 100V ± 10% at 50/60Hz, 40VA. Physical characteristics (excluding accessories) Dimensions 300 mm (11.8 in.) wide...

  • Page 8: Accessories

    T1500A OPERATOR MANUAL ACCESSORIES Standard Accessories Probe set MMP159 Test clip set ACC110 (Red) ACC111 (Black) Operator manual MAN151 SYMBOLS CAUTION To prevent damage to this product and to ensure its safe use observe the specifications given in this manual when connecting to terminals marked with this symbol.
  • Page 9 Connecting the T1500A to a power supply. ASA DEVICE TESTING Information about the different ways in which the ASA facilities of the T1500A can be used and how to test devices. ASA SEMICONDUCTOR TESTING Describes methods of testing signal diodes, zener diodes, LEDs and transistors in circuit.

  • Page 10: Table Of Contents

    SECTION 3 – INSTALLATION AND SET-UP ............3-1 PREPARATION FOR USE ..................3-1 3-1 Unpacking ....................3-1 3-2 Connecting the T1500A to a power supply..........3-1 3-3 Setting up the T1500A................3-2 3-4 Connecting the test cables ................. 3-3 Single Channel Applications ..............3-3 Dual Channel (Comparison) Applications ..........
  • Page 11 CONTENTS SECTION 4 – ASA DEVICE TESTING..............4-1 TESTING COMPONENTS ..................4-1 4-1 ASA techniques..................4-2 Troubleshooting without documentation ............ 4-2 Typical faults ....................4-3 4-2 Testing resistors ..................4-4 4-3 Testing capacitors ..................4-6 Choosing capacitor testing ranges............. 4-7 Leakage current in capacitors.

  • Page 12: Section 1 - Introduction

    (AC) drive voltage across the component and monitoring the resultant current flow to display impedance signatures. Signatures for different types of components have distinctly different shapes that can be easily distinguished. The inclusion of two channels in the T1500A allows the user to compare the behaviour of two devices simultaneously.

  • Page 13: Section 2 - General Description

    The IEC power connector and power ON/OFF switch are mounted on the rear of the instrument. 2-2 Producing signatures The T1500A applies an alternating voltage to a component or circuit and displays the resulting current versus voltage display on a CRT screen. The voltage applied across the component is displayed horizontally, the current through the component is displayed vertically, so the resulting V/I graph represents the resistance, or impedance, of the component.

  • Page 14: Four-Quadrant Signatures

    Horizontal (Voltage) Axis 3rd Quadrant 4th Quadrant Figure 2-1 The T1500A CRT Display 2-3 Four-quadrant signatures Impedance signatures are graphs of current against voltage, plotted on a scale which has its origin at the centre of the CRT display screen.

  • Page 15: The T1500A Equivalent Circuit

    , and the component under test by a simple impedance, Z (Figure 2-2). Figure 2-2 T1500A equivalent circuit The T1500A contains circuits which measure the voltage across, and the current through, the component to be tested and output a display on the CRT. The voltage, V...
  • Page 16 T1500A OPERATOR MANUAL Figure 2-3 shows the signatures of two resistors, measured on the same voltage range, superimposed. Component B has a greater resistance then component A. Figure 2-3 T1500A display showing two impedance signatures...

  • Page 17: Section 3 - Installation And Set-Up

    Note: If the instrument has been shipped or stored in a cold environment, allow the instrument to reach the temperature of its new location before applying power. 3-2 Connecting the T1500A to a power supply Refer to the voltage label on the rear panel of the instrument and make sure that the marked rating is suitable for the local mains power supply.

  • Page 18: Setting Up The T1500A

    3-3 Setting up the T1500A 1. Connect the power cord to the T1500A and to the power supply and switch on (the power switch is located at the rear of the instrument). The screen should display the Channel A and B outputs (two horizontal traces) about the screen centre.

  • Page 19: Connecting The Test Cables

    INSTALLATION AND SET-UP 3-4 Connecting the test cables Single Channel Applications With the Red probe connected to the Channel A (or Channel B) socket, and the Black probe to the COM socket connect the probes across the device. When checking a signature at a node in a circuit it will often be appropriate to connect the COM socket to a convenient ground point using either a probe or test clip.

  • Page 20: Section 4 - Asa Device Testing

    SECTION 4 – ASA DEVICE TESTING TESTING COMPONENTS Using the Analog Signature Analysis method, safe, low power drive voltages are applied to components to produce "impedance signatures" on the oscilloscope screen. Impedance signatures are graphs of current against voltage, plotted on a scale which has its origin at the centre of the screen.

  • Page 21: Asa Techniques

    T1500A OPERATOR MANUAL All signatures are contained within the diamond shaped area formed by the “load lines” joining the ends of the marked axes. 4-1 ASA techniques The most effective way to use ASA is by comparison with a known good or reference board.

  • Page 22: Typical Faults

    TESTING COMPONENTS Typical faults It is worth keeping in mind that faults are not confined to the "high technology" areas of the board. Most faults will be in the "low technology" sections, e.g. intermittent connections, "dry" solder joints, reversed diodes. For instance, the following faults are equally likely: an open circuit relay coil, a broken trace on a printed circuit board,...

  • Page 23: Testing Resistors

    T1500A OPERATOR MANUAL 4-2 Testing resistors The signature produced by a pure resistance is an inclined straight line whose slope (gradient) is dependent on the value of resistance. Testing resistors is performed by connecting the probes across the device and observing the slope of the displayed signature.
  • Page 24 TESTING COMPONENTS Figure 4-2 2K Resistor Logic Range Low Frequency. Figure 4-3 10K Resistor Med Range Low Frequency Figure 4-4 270K Resistor Med Range Low Frequency...

  • Page 25: Testing Capacitors

    T1500A OPERATOR MANUAL 4-3 Testing capacitors Due to their energy storage characteristics, reactive components produce a phase shift between voltage and current flow. This is displayed as a circular or elliptical signature. See Figure 4-5. Signature of a good capacitor...

  • Page 26: Choosing Capacitor Testing Ranges

    TESTING COMPONENTS Choosing capacitor testing ranges Capacitor signature shapes can vary between a virtually horizontal line for low values of capacitance through the range of ellipse shapes (including a circle) to a line that is almost vertical for high capacitance values. Using the higher frequency ranges will cause greater vertical deflection and make subtle differences in signatures easier to detect.

  • Page 27: Leakage Current In Capacitors

    (R is effectively open circuit). The T1500A causes current to flow through both the capacitance and the parallel resistance. The resulting signature will be the sum of the resistive and capacitive components – Figure 4-9.

  • Page 28: Capacitors In Circuit

    TESTING COMPONENTS Figure Signature of a "leaky" capacitor Note the tilt in the ellipse. This is due to resistive current in the capacitor and indicates a faulty capacitor. In general, if the leakage current in a capacitor is significant compared with the capacitive current, the elliptical signature will be tilted.

  • Page 29: Inductors

    T1500A OPERATOR MANUAL 4-4 Inductors Inductive reactance is dependent on the inductance value of the coil and the frequency of the applied voltage, not the "ohmic" resistance of the coil. The magnitude of the current flowing depends on: 1. The inductance of the coil 2.
  • Page 30 TESTING COMPONENTS Figure 4-10 shows the signature of a ferrite transformer primary winding with the test voltage range set Low and test frequency set High . This demonstrates the effect of a significant value of resistance causing the inductive ellipse to be tilted. Figure 4-11 shows a similar (defective) transformer with a shorted turn.

  • Page 31: Section 5 - Asa Semiconductor Testing

    SECTION 5 – ASA SEMICONDUCTOR TESTING USING ASA TO TEST SEMICONDUCTORS 5-1 Diodes, LEDs and Zeners When forward biased, a diode exhibits a low resistance and a voltage drop of approximately 0.6V. This produces a signature that is an almost vertical trace close to the Y axis (see Figure 5-1).
  • Page 32 T1500A OPERATOR MANUAL Figure 5-1 Signal diode Logic Range Low Frequency Figure 5-2 8.2V Zener diode Med Range Low Frequency...

  • Page 33: Testing Transistors In Circuit

    In many fault finding situations it may not be possible or practicable to remove a device from circuit. The T1500A can be used to test transistors as described in this section. A transistor contains two semiconductor junctions connected "back-to-back" (one between base and collector, the other between base and emitter).
  • Page 34 T1500A OPERATOR MANUAL Figure 5-3 NPN Transistor base-emitter Med Range Low Frequency Figure 5-4 NPN Transistor base-collector Med Range Low Frequency Figure 5-5 NPN Transistor emitter-collector Med Range Low Frequency...

  • Page 35: Field Effect Transistors (Fets)

    TESTING SEMICONDUCTORS 5-3 Field Effect Transistors (FETs) Junction FETs (JFETs) The junction field effect transistor (JFET) consists of a bar of semiconductor material (the “channel”) and a region doped with material of the opposite semiconductor type to the channel (the “gate”). The gate forms a diode junction with each end of the channel (the “source”...
  • Page 36 T1500A OPERATOR MANUAL Figure 5-6 74LS00 Logic Range Low Frequency Input to ground Figure 5-7 74LS00 Logic Range Low Frequency Output to ground Figure 5-8 74LS00 Logic Range Low Frequency Vcc to ground...
  • Page 37 TESTING SEMICONDUCTORS Figure 5-9 74HC02 Logic Range Low Frequency Input to ground Figure 5-10 74HC02 Logic Range Low Frequency Output to ground Figure 5-11 74HC02 Logic Range Low Frequency Vcc to ground...
  • Page 38 T1500A OPERATOR MANUAL Figure 5-12 4017 Logic Range Low Frequency Input to ground Figure 5-13 4017 Logic Range Low Frequency Output to ground Figure 5-14 4017 Logic Range Low Frequency Vcc to ground...
  • Page 39 TESTING SEMICONDUCTORS An example of a defect in an IC is shown in Figures 5-15 and 5-16. Figure 5-15 shows the signature between input and ground of a good IC type 7650 tested in circuit. Figure 5-16 shows the signature of a defective 7650 in the same circuit, where the input protection diode has become leaky.

  • Page 40: Testing Devices In Circuit

    T1500A OPERATOR MANUAL 5-5 Testing Devices in Circuit When testing a component in circuit, the signature is a composite of that device and other components in parallel. This is most often the case when diagnosing faults in service. The characteristic signature at any probing point in a circuit is unique for that circuit.
  • Page 41 TESTING SEMICONDUCTORS Figure 5-18 Signature at secondary winding good circuit Figure 5-19 shows the effect on the signature in Figure 5-18 when one diode (D3) develops a short circuit. During the positive half cycle of the drive voltage (right quadrant) the signature is effectively that of diode D1.
  • Page 42 T1500A OPERATOR MANUAL Figure 5-20 shows the effect of superimposing two signatures to aid comparison diagnosis. Note: When comparing the signatures of two circuits ensure that both circuits are connected to COM at the equivalent circuit points. Figure 5-20 7650 in circuit...

  • Page 43: Testing Bus-Connected Devices

    /CE (Chip Enable) or /OE (Output Enable). This provides a method for looking at the ICs individually. Instead of connecting the T1500A's COM input to Vcc or ground, connect it to the defective bus line. Probe each of the devices' /OE or /CE pins, looking for a device whose signature differs from other similar devices.

  • Page 44: Section 6 - Simple Maintenance And Cleaning

    Cleaning Clean the T1500A with a cloth lightly moistened with water with a small amount of mild detergent. Alternatively, a cloth lightly moistened with alcohol (ethanol or methylated spirit) or isopropyl alcohol (IPA) may be used.

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