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T&M Tools for Field Engineers

Being an electronics/electrical field engineer is a challenging job, and for a person engaged in this job T&M tools are just like weapons to a warrior in the war field. in many cases in india, people rely on ‘jugad’tools for a lot of test and measurement activities, but those are neither safe, nor accurate. So presented here are all the must-have tools for an electronics field engineer to perform his jobs safely and accurately.

Field engineers can work in a variety of jobs. They are specialists employed at companies that offer services to clients, and usually work in the field, i.e., locations owned by the client and not by the company at which they are employed. The locations can range from various production facilities and plants to oil fields. In the field, they can act as service representatives, oversee operations, install equipment and maintain and repair the existing equipment or supervise all engineering operations.

A lot of times in India, we see field engineers with strange tools such as a bulb holder connected to two wires for testing the continuity. These tools may do the job but are not safe and accurate. So here we present some basic tools for field engineers and discuss why and how they are used.

Clamp meter

Flow of electrical charge (current) is used to power everything from appliances at home to huge machinery at various industries. In cases where electricity-powered equipment need to be repaired, serviced, maintained or installed, clamp meters can be indispensable tools. A clamp meter is a device that measures various properties of an electrical current. It is a preferable device in the field due to its numerous advantages, including safety, efficiency, versatility and convenience. When clamp meters are used, you do not need to cut any wires, lowering the chances of fatal shocks. Clamp meters can give accurate readings, allowing engineers to quickly diagnose and resolve most problems. Fig. 1 shows a clamp meter.

A clamp meter

Fig. 1: A clamp meter

 

A clamp meter measures current, voltage, crest factor and continuity. AC current is the primary measurement that a clamp meter should be able to perform. These measurements are taken from different branches of a distributed system to debug the issue.

If an appliance is not working, the first thing to check is the input supply. Most clamp meters are capable of reading AC and DC voltages. These meters can also read crest factor which refers to the measurement of a waveform. The crest factor value is determined by the waveform's peak value versus its RMS value and is important in determining whether a circuit is overloaded. Continuity can also be checked using a clamp meter and the same is indicated with a beeprs. Table I shows various clamp meters available from different manufacturers. 

TABLE I. Clamp Meters from Different Manufacturers

Specifications

 

Fluke Fluke 362

Agilent U1211A

HIOKI 3288-20

Metrix+ Mod: 4250T

IDEAL 61-775

AC current

Range

200A

40A/400A/400-700A/700-1000A

100/1000A

1000A

0.0-999.9A

Resolution

0.1A

0.01A/0.1A/1A

0.1A (100A range)

1A

 

Accuracy

2% ±5 (45-65Hz)

2.5% ±5 (65-400Hz)

1.0 % +5 (400-1000A)

1.5% ±5 digits

2% ±5 digits

2%

DC current

Range

200A

40A/400A/1000A

100/1000A

1000A

0.0-999.9A

Resolution

0.1A

0.01A/0.1A/1A

0.1A (100A range)

1A

 

Accuracy

2% ±5 digits

 

1.5% ±5 digits

2% ±5 digits

2%

AC voltage

Range

600V

400V/1000V

4.2/42/420/600V

400mV-700V

0.0-750.0V

Resolution

0.1V

0.1V

0.001V (4.2V range)

1V

 

Accuracy

1.5% ±5 (45-400Hz)

1 % ±5 digits

2.3% ±8 digits

1.5% ±5 digits

1%

DC voltage

Range

600V

400V

420m/4.2/42/420/600V

400mV-1000V

0.0-999.9V

Resolution

0.1V

0.1 V

0.1mV (420mV range)

1V

 

Accuracy

1% ±5 digits

0.5% ±5 digits

1.3% ±4 digits

1% ±3 digits

1%

Resistance

Range

300/3000Ω

4000/ 4kΩ

420-41.99MΩ

400Ω-40MΩ

0.0-999.9 0hm

Resolution

0.1/10

0.1Ω/0.001kΩ

0.1Ω (420Ω range)

10kΩ

 

Accuracy

1% ±5 digits

0.5% ±3 digits

2% ±4 digits

1.5% ±5 digits

2%

Continuity

 

≤700

Yes

Yes

Yes

Yes

Dimensions

 

205x60x22mm

106x273x43mm

57x180x16mm

249x89x38mm

270x103x48.5mm

Clamp opening

 

18mm

52mm

35mm diameter

52mm

51mm

Weight (gm)

 

196

625

150

360

500 (including battery)

Safety reading

 

CAT III 600V

CAT III 1000V/CAT IV 600V

CAT III 600V (current) CAT III 300V (voltage)

IEC 61010-1

CAT IV, CAT III

 

Insulation resistance tester

Eighty per cent of electrical maintenance and testing involves evaluating insulation integrity. Harsh installation environments, especially those with extreme temperatures and/ or chemical contamination, cause deterioration to the insulations and, as a result, personnel safety and power reliability can suffer.

So it is important to identify this deterioration as quickly as possible so you can take the necessary corrective measures. Fig. 2 shows an insulation resistance meter.

Insulation resistance meter

Fig. 2: Insulation resistance meter

 

To test the insulation, we apply a highly regulated, stabilised DC voltage across a dielectric and measure the amount of current flowing through that dielectric, and then calculate the insulation resistance using Ohm's law. The current here is the leakage current and the resistance is in mega ohms. This value of resistance is used to evaluate the integrity of the conductor.

Generally, positive and negative leads are put across an insulation barrier. A third lead, which connects to a guard terminal, may or may not be available with every tester. After the connections are made, test voltage is applied for a minute, which is a standard industry parameter that allows you to make relatively accurate comparisons of readings from past tests done by other technicians. During this interval, the resistance reading should drop or remain relatively steady.

Larger insulation systems will show a steady decrease, whereas smaller systems will remain steady because the capacitive and absorption currents drop to zero faster than on larger systems. After one minute, you should read and record the resistance value. Table II shows insulation resistance testers from different manufacturers.

TABLE II. Insulation Resistance Testers from Different Manufacturers

Specifications

 

Fluke Fluke 1507

IDEAL Model: 61-797

HIOKI IR4056-20

Metrix+ DIT 3125

Insulation secifications

Measurment range

1507: 0.01MQ-10GΩ

Up to 20GΩ

Up to 4000MΩ

0-1000GΩ

Test voltage

50V, 100V, 250V, 500V, 1000V

50V, 100V, 250V, 500V, 1000V

50V, 100V, 250V, 500V, 1000V

30-600V

Test voltage accuracy

+20%, -0%

0-20%

2% ±5 digits

2% ±3 digits

Short circuit current (mA)

1mA nominal

1mA nominal

1.2mA or less

1.3mA

Auto discharge

Discharge time <0.5 seconds for C = 1μF or less

Discharge time <1 second for C <1μF

Yes

Yes

Maximum capacitive load

Operable with up to 1μF load

Operable with up to 1μF load

Not specified

AC 1200V/10 sec

Measure accuracy

±3% +5 (below 100V)

-

4%

>100GΩ ±20%

Earth-bond resistance measurement

     

Range

20Ω/200Ω/2000Ω/20kΩ

 

10-1000Ω

 

Resolution

0.01Ω/0.1Ω/1.0Ω/0.01kΩ

0.01 ohm to 40.00 kΩ

0.01 Q (10Ω range)

 

Accuracy

±(1.5% +3)

 

3% ±2 digits

 

Overload protection

2V RMS or DC

600V AC RMS/DC

600V AC

 

Open circuit test voltage

>4.0V, <8V

>4.0V, <8V

4.0V to 6.9V

 

Short circuit current

>200.0mA

>200.0mA

200mA or more

 

Safety

 

Complies with ANSI/ISA 82.02.01 (61010-1) 2004, CAN/ CSA-C22.2 NO. 61010-1-04, and IEC/EN 61010-1 second edition for measurement category IV 600V (CAT IV)

Complies with UL/IEC/EN 61010-1, 61010-031, EN61557, EN 61326-1 +1A (EMC) Cat IV-600V

CAT III 600V

IEC 61010-1

IP rating

 

IP40

-

 

IEC 60529 (IP40)

Dimensions

 

203x100x50mm

207x95x52mm

159x177x53mm

153x213x95

mm

Weight (gm)

 

550

630

600

1030

 

Earth ground tester

A proper grounding system is of huge importance in the industrial and home environment. Proper grounding of metallic enclosures and support structures that are part of the electrical system helps avoid fatal shocks due to any kind of electrical system failure. The grounding system also provides protection against static electricity from tribocharging. Another important use of grounding system is protection against direct lightning strokes.

It is estimated that at least 15 per cent of the power quality problems are related to improper grounding. Therefore good grounding ensures that these problems do not escalate. Fig. 3 shows an earth ground tester and table III shows the testers from different manufacturers.

Earth ground tester

Fig. 3: Earth ground tester

 

TABLE III. Earth Ground Testers from Different Manufacturers

Specifications

 

Fluke Fluke 1621

Metrix+ Model: DET 1503

IDEAL 61-920

General specifications

Measuring functions

Three-pole earth ground resistance, two-pole AC resistance of a conductor, interference voltage

0.00-2000Ω

Ground resistance, ground leakage current

Measuring rate

Two measurements/second

5sec/V 2sec

0/120/1200Ω

Safety

IEC/EN 61010-1, 600V CAT II, pollution degree 2

IEC 61010-2­031

IEC61010-1: 2001 (CAT IV 300V Pollu­tion degree 2), IEC61010-2-032: 2002

IP rating

IP 40; IEC/EN 60529

IEC60529 (Ip54)

IP 40

Dimensions

113x54x216mm including holster

170x120x79mm

246x119x53mm

Weight (gm)

850

675

771

Electrical specifications

Test voltage

3.7kV

0-200V

-

Measuring time

8 seconds (average from when start is pressed)

10 sec-10 min

-

Electromagnetic compatibility

Emission: IEC/EN 61326 Class B, Immunity: IEC/EN 61326 Annex C

Yes

-

Interference voltage display

Vmax 30Veff

Common mode rejection >80dB at 50Hz and 60Hz Ri 680kΩ

Measuring uncertainty <10% for pure AC and DC signals

Yes

Yes

Measuring range resolution

 

Resolution 0.01Ω, display range 0-19.99Ω

0.01Ω

 
 

Resolution 0.1Ω, display range 20-199.9Ω

0.1Ω

 
 

Resolution 1Ω, display range 200-1999Ω

 

RE resistance measurement

Open circuit voltage (Vac)

23V to 24V AC

220V

-

Short circuit current (mA)

>50mA AC

1.3mA

0.1mA

Measuring frequency (Hz)

128Hz

50/60Hz

2400Hz

Permissible overload (Veff)

250Veff

300V AC 30 seconds

-

 

Laser distance meter

Laser distance meter can be a very useful tool for measuring distances with good precision without physical contact. In fact it allows for the most sensitive and precise length measurements, faster recordings encompassing large ranges. All these qualities do not come with a single technique so different techniques are used based on specific requirements. Some of the most important techniques used for laser distance meters are as follows:

1. Triangulation is a geometric method, useful for distances in the range of a millimetre to many kilometres.

2. Time-of-flight measurements (or pulse measurements) are based on measuring the time-of-flight of a laser pulse from the measurement device to some target and back again. Such methods are typically used for large distances.

3. The phase-shift method uses an intensity-modulated laser beam. Compared with other techniques, its accuracy is lower, but it allows unambiguous measurements over larger distances and is more suitable for targets with diffuse reflection.

4. Frequency modulation methods involve frequency-modulated laser beams, for example, with a repetitive linear frequency ramp. The distance to be measured can be translated into a frequency offset, which may be measured via a beat note of the sent-out and received beam.

Fig. 4 shows a distance meter.

Distance meter

Fig. 4: Distance meter

 

Vibration tester

Machines are used in nearly every aspect of our daily life; from the vacuum cleaner and washing machine we use at home, to the industrial machinery used to manufacture nearly every product we use on a daily basis. When a machine fails or breaks down, the consequences can range from financial loss, personal injury and possible loss of life. For this reason, early detection, identification and correction of problems is paramount to anyone involved in the maintenance of industrial machinery to ensure continued, safe and productive operation.

Vibration levels give a very good idea of the state of a machine. It is evident from the fact that we naturally touch a rotating machine and feel the vibrations to see if it is running right. Even machines in the best of operating condition will have some vibration because of small, minor defects. Therefore each machine will have a level of vibration that may be regarded as normal or inherent. However, when vibration increases or becomes excessive, some mechanical trouble is usually the reason. Various instruments have been developed to actually measure a machine's vibration level and assign it a numerical value. Fig. 5 shows a vibration meter and Table IV shows features of some vibration meters from different manufacturers.

Vibration meter

Fig. 5: Vibration meter

 

TABLE IV. Vibration Meters from Different Manufacturers

Specifications

 

Fluke Fluke 805

MetrixTM Model: VB 8202a

MCM Instruments vibration tester AVD - 80

Extech Instruments Extech 407860

Range

Low frequency

10Hz-1000Hz

10Hz

10Hz

10Hz

High frequency

4000Hz-20,000Hz

1000Hz

1000Hz

1000Hz

Vibration limit

 

50g peak (100g peak-peak)

0.1-4000Ω

 

200mm/s

Sample rate

Low frequency

20,000Hz

10Hz

  

High frequency

80,000Hz

1000Hz

  

Signal-to-noise ratio

 80dB  

Sensor

Sensitivity

100mV g ±10%

Piezoelectric

  

Measurment range

0.01g-50g

0.1-400.0 m/s

  

Resolution

0.01g

 

0.1mm/s

0.5m/s2, 0.5mm/s, and 0.05mm

Safety

Accuracy

At 100Hz ±5% of measured value

5% ±2 digits

±(2% + 0.1mm/s)

±5% ±2 digits

IP rating

 

IP54   

Dimensions

 

241x71x58mm

140x70x30mm

 

180 x 72 x 32mm

Weight (gm)

 

1160

150

200

395

 

These are all the basic equipment that a field engineer would need depending on the project at hand. You can also add a multimeter to the list, which is also a useful tool in many cases. Refer buyers' guide on handheld digital multimeters published in Feb ruary 2013 issue for details.

Author: Ankit Gupta