thereafter,  he  touched  the  ground  lead  and received a serious shock. He was treated for minor burns on the palm.” VOLTAGES ABOVE 300 VOLTS All the safety procedures for measuring voltages below 300 volts also apply when you are measuring voltages above 300 volts. However, the big difference when measuring voltages above 300 volts is that you must NOT hold the test probe while the equipment is energized.  Instead,  you  must  attach  the  test  probes while the equipment is de-energized. (Refer to table 3-5). ELECTROSTATIC DISCHARGE PRECAUTIONS Electrostatic  discharge  (ESD)  can  destroy  or damage  many  electronic  components,  including integrated circuits   (ICs) and discrete semiconductor devices. Since certain devices are more susceptible to ESD damage than others, warning symbols, shown in figure  3-1,  are  now  used  to  identify  ESD-sensitive (ESDS)  items.  The  widespread  use  of  integrated circuits  led  to  the  development  of  special  training courses  in  miniature/microminiature  (2M)  circuit repair. Certified 2M technicians are trained in procedures for  reducing  the  causes  of  ESD  damage.  The procedures are similar for all levels of maintenance. If you are certified in 2M repair, you should follow the protective measures in table 3-6 to help prevent ESD damage.  Remember,  although  many  sources  of electrostatic  charge  are  of  little  consequence  during most daily activities, they become extremely important when  you  work  with  ESD  material.  If  you  are  not certified in 2M repair, do not attempt to repair any of these circuits. For  further  information  on  handling  ESD materials,  refer  to  Introduction  to  Microelectronics, Navy  Electricity  and  Electronic  Training  Series (NEETS), Module 14, NAVEDTRA 172-14-00-84. Q3.    What  is  the  FIRST  step  in  taking  voltage measurements below 300 volts? Q4.    What is the major difference between using a test probe to measure a voltage above 300 volts and using it to measure a voltage of 300 volts or less? Q5.    What dangerous effect to electronic components are  EDS  precautions  designed  to  reduce  or eliminate? ELECTROMAGNETIC RADIATION HAZARDS The  electromagnetic  spectrum  encompasses everyday  uses  from  commercial  power  to  medical 3-5 No. Safety Precaution 1 ALWAYS follow all preliminary safety procedures for measuring voltages below 300 volts before beginning your measurement. 2 ALWAYS make sure that the equipment you are working on is de-energized. 3 ALWAYS follow the tag-out procedures. 4 ALWAYS discharge all high-voltage capacitors with a shorting probe. 5 ALWAYS attach the ground probe of the measuring device first. 6 ALWAYS secure the other probe of the measuring device to the test point to be measured. 7 ALWAYS make sure that the measuring device is set up for the voltage level and polarity to be measured. 8 ALWAYS energize the equipment under test, make the measurement, and then de-energize the equipment. Table 3-5.—Safety Precautions For Measuring Voltages Above 300 Volts