Multitester Electronic Measuring Device - Coursework Example

Also known as a Multitester or a Volt-Ohm meter (VOM), a multimeter is an electronic measuring device that merges various measurement units (voltage, current and resistance) into one component. It is one of the most common test equipment in the electronics industry. Initially, analogue multimetres were used for testing electronics, but this was later replaced by digital multimeters which have a variety of functions and an increased level of precision (Kalsi, 2010). Safety is critical when operating any apparatus involving electricity. For this reasons, I have prepared a digital multimeter user safety guide to enlighten users of digital mulitmeters on how to handle and maintain the multimeter as well as how to ensure safety when using it. This user manual was prepared using data gathered from internet sources. Moreover, a professional electrician was also consulted to advice on the most suitable DMM as well as give information about safe usage of the DMM. This report will first give a brief introduction about the multimeter, its uses and its components, then give a detailed description about testing and using the multimeter. The main target audience of this user guide are people with basic knowledge about electricity but have never used a multimeter. This user guide will make use of various graphics aimed at enlightening the user of the various parts of the device and their key functions. Users are advised to read and follow the instructions, precautions and warnings in this user guide in order to use the DMM correctly and safely. Introduction A digital multimeter (DMM) is a very essential tool when resolving an electrical fault. It differs from its predecessor, the analogue meter- which has a needle and a gauge, in that it has a LCD display and an improved level of accuracy. A DMM is capable of working with both energized and de-energized electrical circuits. It also has a diversity of other functions useful to both professional users and amateurs. The functions include measuring voltages and currents (both AC and DC), continuity, capacitance, resistance, frequency and transistor tests. Guide to choosing a Digital Multimeter When selecting test equipment, the decision should be based on the type of electrical measurement to be measured. A DMM is should be selected when measuring small value measurements as it is accurate within 0.1 – 0.5 % of the reading. Other features to look for are dialing or auto ranging, which enables you to move between different measuring ranges to show the most significant digits and auto polarity which shows whether the current being measured is positive or negative (Draper Tools Limited, 2005). For the purpose of this report, I chose the Draper 787993 Digital Multimeter due to its portability, affordability, safety and multi-functions. This DMM has 3 main parts, the LCD screen, 2 leads and a function range selector (Draper Tools Limited, 2005). General Safety considerations when using a DMM Never Attempt to measure high or unknown voltages Measure current with the DMM parallel to the circuit Touch and metal parts of the test assembly Connect the test leads to a live circuit before assembling the DMM Measure voltage or current that exceeds the limits of the DMM Ground yourself when taking electrical readings. Meter Markings and Symbols Symbol Function Symbol Function Caution, Refer to the user Manual for more information Unit of measuring resistance (OHMS) Indicates that the DMM’s battery voltage is low Audible Continuity range Indicates a warning, risk of electric shock Units of measuring Current (AMPS) Diode Check Units of measuring Voltage (Volts) Parts of the TPI 135 Digital Multimeter 1. LED Display 5. Positive Jack Test Lead 2. Function Range Selector Switch. 6. Data hold Button 3. COM Socket for the Negative Test Lead 7. Back Light Button 4. 10A Jack socket for the Positive test lead 8. Positive (Red) and Negative (Black) Test Leads Comparison between the Analog and Digital Multimeter As discussed earlier, there are two types of multimeters, analog and digital multimeters, where each type has its own pros and cons. Analogue Multimeters Digital Multimeters They display the value of the results with a needle set over a scale as shown below. They display the output as a numerical figure on a LCD display Advantages Advantages More accurate when measuring varying voltage as the meter’s needle gives continuous movement (Kalsi, 2010). More accurate than analog multimeters as they display digital numerical feeds, specific and readable up to decimal points. Using the Draper 787993 Digital Multimeter Before using this DMM, it is important to first connectors and test leads for any damage and replace any defective leads. It is also essential to read and understand the safety rules and operating instructions before using the DMM (Draper Tools Limited, 2005). (a) Measuring DC Voltage Caution Never measure DC voltages if the circuit has a motor that is being turned ON or OFF as this may cause large voltage surges and may damage the meter. When measuring an unknown voltage, set the selector switch at the highest range until a reasonable reading is obtained. Procedure 1. Set the function switch at the maximum DC Volt Position shown below 2. Plug the black test Lead into the Negative COM jack and the reed lead in the positive jack. 3. Touch the black lead on the negative side of the circuit/battery and the red lead on the positive side as in the figure below. 4. Read the voltage shown on the display. You may switch to lower voltages to obtain a higher resolution reading. (b) Measuring AC Voltage Caution There is always a high risk of electrocution when measuring AC Voltage (Professional Equipment, 2012). Procedure 1. Set the function switch to the maximum AC voltage position shown below 2. Repeat steps 2 – 4 in (a) above. (c) Measuring DC Current Caution The Test leads must be connected in series with the circuit when measuring DC current. Never attempt to measure current with the leads connected in parallel with the circuit. Procedure 1. Disconnect the power from the circuit to be measured 2. Insert the black test lead into the COM jack and the red lead into the 10A jack. 3. Set the function range selector to the desired range depending on the current to be measured 4. Connect the test leads to the circuit to be measured (in series) 5. Connect power back to the circuit 6. Read the current reading on the multimeter’s LCD display (d) Measuring resistance Caution Never measure the resistance of an energized circuit. For best results, remove the resistor from the circuit before measuring (Extech Instruments, 2007). Procedure 1. Plug the black test lead into the COM jack and the red lead into the positive jack 2. Set the rotary switch to the highest range in the OHM function 3. Connect the test leads to the circuit or resistor to be measured 4. Read the value of resistance on the display. Set the rotary switch to a lower position in order to get a more accurate reading. (e) Checking Continuity Caution To prevent electric shock, never measure continuity on circuits that have voltage. Procedure 1. Set the rotary switch to the position shown below 2. Plug the black lead into the COM jack and the positive lead into the Positive jack 3. Connect the test leads to the circuit or wire you wish to test 4. The Multimeter will produce an audible sound, but if the circuit is broken, the LCD display will indicate a ‘1’ (Extech Instruments, 2007). (f) Measuring a diode Procedure 1. Plug the black lead to the COM jack and the red lead to the V jack. 2. Position the selector switch to the position 3. Connect the black lead to the diode’s cathode and the red lead to the anode 4. The forward voltage drop in mV will now be indicated in the display. If the diode is reversed, a ‘1’ will be indicated on the display (Draper Tools Limited, 2005). Maintaining the DMM 1. The DMM meter battery will need replacement when a appears on the display 2. When replacing a fuse, open the meter casing and replace the blown fuse with another one of the same type and value Caution To prevent the risk of electric shock, ensure that you disconnect the test leads before opening the meter casing (Professional Equipment, 2012). Written Statement Most of the information used for compiling this user guide was collected from various internet sources, by searching various keywords on search engines search as Google. The detailed research was aimed at ensuring that this user guide meets the required safety standards and can be used by users who have never used a Digital Multimeter before. This report also has an introduction which is aimed at giving first time users a brief overview of the multimeter and its various uses. After the user guide was compiled, it was reviewed by a professional electrician who suggested that it was important to include a section discussing about how to maintain a mulitmeter. According to the electrician, this section is also essential for first time users and as a result I included it in the user guide. The electrician’s review was important as it also enabled me to spot and fix various errors that were initially present in the user guide. Conclusion There are various types of multimeters which come in various types and all serve varying functions. The choice on the type of multimeter to purchase solely depends on the user’s budget and intended purpose. This user guide aims at guiding users about how to choose the most suitable multimeter as well as how to use the meter safely and effectively. When using a multimeter, users are advised on the importance of handling and maintaining the device according to the manufacturer’s instructions. First time users are advised to read through this guide before using the DMM in order to avoid damaging the equipment or even injuring themselves. Bibliography Draper Tools Limited, 2005. Instructions for Digital Multimeter [pdf] Available at: < http://www.tooled-up.com/artwork/ProdPDF/78993ins.pdf > [Accessed 19 February 13]. Extech Instruments, 2007. Digital Multimeter User’s Guide [pdf] Available at: . [Accessed 19 February 13]. Kalsi, H.S., 2010. Electronic Instrumentation. Nodia: Tata McGraw-Hill Education. Professional Equipment, 2012. Guide to Multimeters. [ONLINE] Available at: [Accessed 19 February 13]. Read More