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4 Level 1 Pre Job Briefing Location Nearest Medical Facility1042 W Hamlet AVE; Hamlet, NC 28345 Forte Annex at rear of complex Nearest Medical Facility Sandhills Regional Medical Center 1000 W Hamlet Ave; Hamlet, NC 28345 (910) 911 Caller & Backup -- Runner Work Task: EUS-255 Hazards – Mitigation of Risk (PPE) Questions
5 EUS-255 Troubleshooting Digital Multi-Meter (DMM) Jeffrey Wimmer Forte 326
6 DMM Amps A Series Volts V Parallel Ohms Ω Continuity Audible Tone
7 Who makes the rules… Alphabet Soup ANSI, CSA and IEC NIOSH NEMA NFPAOSHA Both employers/employees responsible to know & follow standards. Citations and penalties may be imposed if standards are not observed. NFPA 70E, provide guidance on safety measures and procedures. Key resource - detailed instructions on PPE and safe work procedures required for specific tasks. They do not supplant OSHA. In case of conflict, follow OSHA standards. NIOSH source of electrical safety information, but is not a regulatory agency. ANSI Sets standards for equipment. Employers and technicians should be familiar with ANSI electrical safety standards C and S82.02 and, if applicable, C2-81. IEEE helps calculate arc flash hazard
8 Safety How not to save time...Last known earthly residence of automotive fuse used to replace original fuse How not to save time... This meter had the original fuse replaced with an automotive fuse. When the operator attempted to measure 480 volts with the leads in the amps inputs, the fuse offered no protection. It is better to leave the circuit unfused and open than to use the wrong fuse. Note that the test leads and probes, though damaged, survived more or less intact. This fact, plus the mechanical ruggedness of the meter body, which helped to contain the explosion, contributed to the fact that the operator was not hurt. Test leads survived intact ©2003 Fluke Corporation Electrical measurement safety
9 Safety This DMM had a hot date with 13.8 kV. Test leads destroyed13.8 kV arced over to test probes. This meter accidentally contacted Medium Voltage. The operator worked in a West Virginia mine. He disconnected the 13.8 kV buss bar, but did not know that the buss bar was being fed from another connection. He went to check a control circuit behind the buss bar. When he got close to the buss bar, about 4-6” away, there was an arc-over to his probe tips. The resulting plasma fireball singed his beard, but otherwise did not harm him. When he’d recovered sufficiently, he took the meter back to his distributor to see if the warranty still applied... Insides were barbecued. ©2003 Fluke Corporation Electrical measurement safety
10 Poor quality leads and probes led to injury.Safety 250V fuse didn’t open in time An electrician was loaned this low-cost meter one day because his quality meter was not available. He accidentally went across 480 volts with the leads in the amps jacks. Both fuses are 250 volts. The fuse didn’t open in time to prevent major damage to the meter. However, while the meter is not as dramatically damaged as the previous ones, the electrician was injured - he had severe burns on his forearm, upper arm and shoulder and had his arm in a sling when we met him. A good part of the reason is the cheap quality of the probes and leads (see next slide). Poor quality leads and probes led to injury. Probe tips burned off ©2003 Fluke Corporation Electrical measurement safety
11 Safety Fingerprints burned into probes There are two lessons here:One is that the safety quality of the leads and probes is just as important, if not more important, than that of the meter itself. The other is that it can happen to anyone: this electrician was a seasoned journeyman with 30-odd years of experience. ©2003 Fluke Corporation Electrical measurement safety
12 Measurement Category ANSI, CSA and IEC define four measurement categories of over-voltage transient impulses (voltage spikes). Rule of Thumb Closer technician is working to power source, greater the danger and higher the measurement category number.
13 CATEGORY
14 Dangerous high-energy transient such as a lightning strike will be attenuated or dampened as it travels through the impedance (ac resistance) of the system. CAT I Protected electronic circuits. CAT II Covers the receptacle circuit level and plug-in loads CAT III Distribution level wiring. 480-volt and 600-volt circuits such as three-phase bus and feede circuits, motor control centers, load centers and distribution panels. Permanently installed loads are also. Large loads that can generate their own transients. Trend to using higher voltage levels in modern buildings has changed the picture and increased the potential hazards. CAT IV Origin of installation. This refers to power lines at the utility connection, as well as the service entrance. It also includes outside overhead and underground cable runs, since both may be affected by lightning.
15 Voltage Rating Within CategoryCAT I CAT II CAT III 600V 1000V CAT IV Within a category, higher voltage rating denotes a higher transient withstand rating: CAT III V superior protection CAT III 600 V The real misunderstanding occurs… CAT II V CAT III 600 V superior protection
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17 Look for these safety features in a DMMFused current inputs Use of high-energy fuses (≥ 600 V) High-voltage protection in resistance mode (≥500 V) Protection against voltage transients (≥6 kV) Safety test leads w/ finger guards & shrouded terminals Independent safety organization approval/listing UL CSA
18 17B 87V 1587
19 DMM Pre-Job Inspection Independent Testing and CertificationVerify your test tools have been tested and certified by two or more independent testing laboratories UL in the United States CSA in Canada TUV in Europe
20 DMM Pre-Job Inspection Inspect Your Tools“…tools must be visually inspected frequently to help detect damage and ensure proper operation.” NFPA 70E National Fire Protection Association Case - Cracked, broken Display - Faded Leads & Probes Frayed or broken wires Shrouded connectors Finger guards Minimum exposed metal on probe tips CAT ratings Double insulation • Continuity function check for internal open Check test lead resistance: A: Insert leads in V/W and COM inputs. B: Select W, touch probe tips. Good leads are W.
21 DMM Pre-Job Inspection Supplementary InspectionUsing properly functioning test tools is vital to help protect yourself from possible injury or death. Tools that fail any of these inspections should be replaced with new test tools from a leading manufacturer. • Marked: CAT III, CAT IV, 600 V,1000V, “double insulated” symbol on the back. • Manual: verify that the Ω and continuity circuits protected same level V test circuit • Fuses: A & V of fuses meets specifications Fuse voltage must be as high or higher than the meter’s voltage rating Use meter’s capability ensure fuses in place and functioning per spec 1: Test lead in V/W input. Select W 2: Probe tip into mA input. Read. 3: Probe tip into A input. Read. Fuse should indicate value near zero.
22 ABC’s of DMM Resolution Accuracy Displays Results True-rms
23 Resolution How small a variation can be observed Digits CountsExample: DMM resolution 1 mV on the 4 V range, possible to see a change of 1 mV (1/1000 of a volt) while reading 1 V. Digits A 31⁄2-digit meter can display three full digits ranging from 0 to 9, and one “half” digit which displays only a 1 or is left blank. A 31⁄2-digit meter will display up to 1,999 counts of resolution A 41⁄2-digit meter can display up to 19,999 counts of resolution. Counts More precise description. Today’s 31⁄2-digit meters may have enhanced resolution of up to 3,200, 4,000, or 6,000 counts. For certain measurements, 3,200-count meters offer better resolution. For example, a 1,999-count meter won’t be able to measure down to a tenth of a volt if you are measuring 200 volts or more. However, a 3,200-count meter will display a tenth of a volt up to 320 volts. This is the same resolution as a more expensive 20,000-count meter until you exceed 320 volts.
24 Accuracy Largest allowable error that under specific operating conditions Percent An accuracy of 1% of reading means that for a displayed reading of 100 V, the actual value of the voltage could be anywhere between 99 V and 101 V. Digits Indicates how many counts the digit to the extreme right of the display may vary. ± (1 % + 2) Ergo, for a display reading of 100 volts… …actual voltage would be between 98.8 V and V.
25 Note: Bar Graph - TrendingDisplays Digital High Accuracy Resolution – 3 or more digits measurement Analog Less accurate Great for trending unstable data Prone to damage Note: Bar Graph - Trending
26 Results - Data Capture Manual Auto – Backup? ShareWireless -- SEPERATION Small area networks FLUKE
27 Protection & Control Electric Utility Substation & Relay Technology Team Richmond Community College, Rockingham, NC, March 2017
28 True-RMS? A true-rms (root mean square) device 1 of 3 tools measure ac voltage: Oscilloscope Average-responding digital multimeter (or clamp meter) An average-responding meter uses averaging mathematical formulas to accurately measure pure sinusoidal waves. It can measure nonsinusoidal waves, but with uncertain accuracy. Nonlinear loads such as variable speed drives or computers -- distorted waves can be up to 40% low or 10% high in its calculations. True-rms digital multimeters (or clamp meter) -- measure both sinusoidal and nonsinusoidal Root mean square calculates the equivalent dc value of an ac waveform. it determines the “effective,” or dc heating value, of any ac wave shape. True-rms meter is the better choice for taking measurements on power lines where ac characteristics are unknown.
29 Procedures Amps A Series Volts V Parallel Ohms ΩContinuity Audible Tone
30 Voltage Select V~ (ac) or V (dc), as desired.Plug the black test probe into the COM input jack. Plug the red test probe into the V input jack. If the DMM has manual ranging only, select the highest range so as not to overload the input. Touch the probe tips to the circuit across a load or power source (parallel to the circuit). View the reading, being sure to note the unit of measurement. Note: For dc readings of the correct polarity (±), touch the red test probe to the positive side of the circuit, and the black probe to the negative side or circuit ground. If you reverse the connections, a DMM with autopolarity will merely display a minus sign indicating negative polarity. With an analog meter, you risk damaging the meter. Note: 1/1000 V = 1 mV 1000 V = 1 kV High-voltage probes are available for TV and CRT repair, where voltages can reach 40 kV Caution: These probes are not intended for electrical utility applications in which high voltage is also accompanied by high energy. Rather, they are intended for use in low-energy applications.
31 Resistance Turn off power to the circuit. Select resistance (Ω).Plug the black test probe into the COM input jack. Plug the red test probe into the Ω input jack. Connect the probe tips across the component or portion of the circuit for which you want to determine resistance. View the reading, being sure to note the unit of measurement: ohms (Ω), kilohms (kΩ), or megohms (MΩ). Note: 1,000 Ω = 1 kΩ 1,000,000 Ω = 1 MΩ Make sure the power is off before making resistance measurements.
32 Continuity Set on the lowest ohms range.Ohmmeter will read a very low resistance such as zero ohms. If there is no continuity between two points, the ohmmeter will read infinite ohms.
33 Current Turn off power to the circuit.Cut or unsolder the circuit, creating a place where the meter probes can be inserted. Select A~ (ac) or A (dc) as desired. Plug the black test probe into the COM input jack. Plug the red test probe into the amp or milliamp input jack, depending on the expected value of the reading. Connect the probe tips to the circuit across the break so that all current will flow through the DMM (a series connection). Turn the circuit power back on. View the reading, being sure to note the unit of measurement. Note: If the test leads are reversed for a dc measurement, a “–” will show in the display
34 Common situations leading to DMM failureContact with ac power source while test leads are plugged into current jacks Contact with ac power source while in resistance mode Exposure to high voltage transients Exceeding maximum input limitations (voltage and current)
35 CAUTION Meter ratings and capabilities vary by manufacturer. Before working with a new meter, be sure to familiarize yourself with all operating and safety procedures for that meter contained in the users manual.
36 Recommended Resources•How to Use Your Multitester •Digital Multimeter Principles 4E https://www.amazon.com/Gardner-Bender-Your-Multitester-Book/dp/B000ET0UYI https://www.amazon.com/Digital-Multimeter-Principles-Glen-Mazur/dp/ X
37 Electric Utility Substation & Relay Technology