Issued by <Company Name>Page 1

<Company Name>Procedure Manual

Issue No.9Date: 10 May 2007

Issued by <Company Name>Page 1

LABORATORY

PROCEDURE MANUAL

TABLE OF CONTENTS

1.DC Voltage

1.1.Scope - Automatic generation of D.C. Voltage from 100mV to 1kV.

1.2.Note 6: Loading consideration on the 200mV range of the calibrator

2.DC Resistance

2.1.Scope - Automatic generation of 2 Wire Resistance from 10 to 10M.

2.2.Scope - Automatic generation of 4 Wire Resistance from 0 to 10k.

3.DC Current

3.1.Scope - Automatic generation of D.C. current in up to 2 Amps.

3.2.Scope DC Current Source 2A to 30A

4.A.C. Voltage

4.1.Scope - Automatic generation of A C voltage from 100mV, 40Hz to l kHz.

5.A.C. Current

5.1.Scope - Automated generation of AC current 0uA to 2Amps, 40Hz to 1 kHz

6.AC Current Source 2A to 30A

6.1.Scope - Generation of AC Current from 2A to 30Amps

7.RCD Timer

7.1.Scope - RCD Timer measurement using the 2100/3200

8.Insulation Resistance

8.1.Scope – Insulation Resistance meter calibration using the 2100/3200

9.Loop Impedance Measurement

9.1.Scope – Loop Impedance Measurement using the 2100/3200

10.2100/3200 RCD Timing Test

10.1.Scope - Calibration of Transmille 2100 & 3200 16th Ed Calibrators

1.DC Voltage

1.1.Scope - Automatic generation of D.C. Voltage from 100mV to 1kV.

1.1.1.Equipment

3000 Series CalibratorPrecision Low thermal Lead set

1.1.2.Connection diagram

1.1.3.Measurement Method:

1)Allow all equipment sufficient time to stabilise,

2)Refer to instrument manufactures handbook for operating instructions.

3)Check environmental conditions e.g. mains voltage/frequency, temperature are within laboratories limits

4)Use the low thermal lead set to connect the calibrator’s voltage output terminals to the input instrument under test. (See note 2)

5)Connect guard and earth as required. (See notes below)

6)Check the Zero of the measuring instrument and null if required.

7)Set the output voltage required from the instruments calibration procedure and turn output on. (For automated calibration ProCal will set the calibrator.) Refer to manufacture’s manual for equipment operation.

1.1.4. Note 1: Safety Consideration

The calibrator can generate hazardous voltages and great care must be taken to avoid the risk of shock. The use of shrouded leads, as supplied in the lead set is highly recommended. Note that any capacitance on the output will become charged to the output voltage, and if the calibrator is set to standby will be left charged presenting a shock hazard. Leads must not be connected or disconnected when high voltage is present

1.1.5.Note 1: Calibrator Trips back to standby

The output of the calibrator is shorted or the resistance of the load is too low for the calibrator to drive.

Note that for the 2000 series the factory set for the current limit is set to 10mA for safety reasons, this may be adjusted by internal trimmer up to 25mA if required.

1.1.6.Note 2:Errors due to thermal EMF voltages.

Using the correct test leads is critical for low-level DCV measurements. The 2000 series calibrator’s terminals are gold plated copper and should be mated with the same type, avoid the use of nickel plated brass banana plugs. Thermoelectric voltages occur when different metals at different temperatures are connected together. This property is used in a thermocouple to measure temperature and 10’s of microvolts can easily be generated. To reduce thermal effects minimize the number of connection, use low thermal plugs made from gold and copper, and minimize temperature gradients and keep all equipment at the same temperature.

1.1.7.Note 3: Errors due to common mode voltages and pick up.

It is recommend that the negative side of the calibrator’s output is earthed, an internal relay inside the calibrator can be selected for this, avoiding additional external connections. Letting the output float will allow both terminals to pick up common mode voltages with respect to earth which and may cause noise and unwanted errors in the measuring instrument. It is vet important however to only earth the signal at one place, see Note 3. If the measuring instrument has a guard terminal connect this to the low terminal for the optimum performance when the calibrator’s output is earthed.

1.1.8.Note 4: Errors due to earth & ground loops.

To avoid errors introduced by earth loop’s only earth the output at one point. As there are often voltage drops in mains earth wiring, earthing at the calibrator output and at the measuring input will cause earth current to flow through the connecting lead (which is now in parallel with the mains earth) causing a voltage error.

1.1.9.Note 5: Errors due to Loading.

All voltage sources have output resistance, to which the resistance of connecting leads etc must be added. Most modern measuring instruments are very high input impedance so the loading effects are negligible. Instruments with low input impedance such as thermal transfer standards will load the output and an allowance must be made.

1.2.Note 6: Loading consideration on the 200mV range of the calibrator

The output impedance of the 200mV range on the 2000 series calibrators is 50 ohms. It is important to note this when calibrating moving coil type meters, which have low input impedance. Alternatively the 2Volt range can be used if PC is controlling the calibrator.

1.2.1.Note 7: Errors due Electromagnetic Interference (EMI)

The leads connecting the instruments can pick up both magnet fields generated in all types of mains powered equipment from transformers, motors etc and RF interference from a mobile phone to a noisy switch mode power supply in a computer. Keep wire away from mains conductors and use screened cable to reduce noise on low level signals.

1.2.2.Uncertainties

See spreadsheet

2.DC Resistance

2.1.Scope - Automatic generation of 2 Wire Resistance from 10 to 10M.

2.1.1.Equipment

3000 Series CalibratorPrecision Low thermal Lead set

2.1.2.Connection diagram

2.1.3.Measurement Method:

1)Allow all equipment sufficient time to stabilise as per manufactures handbook.

2)Check environmental conditions e.g. mains voltage/frequency, temperature are within laboratories limits

3)Use a high insulation screened lead to connect the calibrator’s resistance output terminals to the input-measuring instrument under test. (See diagram above)

4)Connect guard and earth as required. (See notes below)

5)Zero the measuring system by shorting the leads together at the calibrator.

6)Set the output required from the instruments calibration procedure and turn output on. (For automated calibration ProCal will set the calibrator) Refer to manufacture manual for equipment operation.

2.1.4. Important: Do not exceed the Maximum Power Rating

Care should be taken that the applied voltages and current do not exceed the calibrator’s specification. Do not connect insulation testers or ductors which test at high currents, exceeding the maximum ratings will damage the resistor and change the resistance value.

2.1.5.Note 1: Errors due to leakage of test leads on high ohms

To ensure accurate readings on high ohms (10megohms and above) use a cable with either Teflon, or polythene insulation. Do not use leads made from PVC or extra flex cable. A cable with 100Gohms insulation resistance will shunt the 1Gohm output by 1%, and the 100Mohm by 0.1%. The screen of the cable should almost always be connected to earth for minimum noise pick up.

2.1.6.Note 2: Errors due to contact and lead resistance on measurements below 1kohm

When measuring resistance with a two-wire connection the resistance of the test leads and connection become very important below 1kohm. Although This resistance can be nulled out, (see note 5) this does not remove contact resistance variation, and in practice it is very difficult to use 2 wire measurements to accuracy better than a few milli-ohms.

It is critical to make sure all connection are clean, and plugs & sockets are not worn or loose fitting.

For accurate low ohm measurements 4-wire Kelvin type connection must be used.

2.1.7.Note 3: Nulling out lead errors

Firstly short the end of the test leads together and ‘zero’ the DMM before connecting them to the calibrator to null out lead and connector resistance out.

The 2000 series calibrators are calibrated for 2 wire ohms as the resistance seen at the terminals.

2.1.8.Note 4: Errors due to Earthing and Guarding.

Earthing the resistance output can sometime introduce more noise on higher values in the reading as in some DMM’s the negative terminal in resistance mode is not the circuit low, but a current sink. Find the best connection by experimentally method. It may be best to connect earth to screen of the test leads and to the DMM’s guard, leaving the resistance measuring circuit to float.

2.1.9.Note 5: Errors due self-heating and voltage coefficients

Measuring resistors at high power levels (above 0.5 watts) will cause the resistor to heat up, due to the temperature co-efficient of the resistor the value will change. As the temperature rise reaches an equilibrium the value of resistance will also stabilise. When the power is removed the resistor will cool down and return to the original value. Generally the resistor should be measured at a power level, which will not cause self-heating, less than 10mW’s for example.

Voltage co- efficient is the change in resistance with voltage, high value film type resistor values will normally reduce at high voltages, and this effect is very small below 200Volts but may need to be considered above this. NOTE the resistors in the 2000 series maximum rating is 200V.

2.1.10.Note 6: Errors due Electromagnetic Interference (EMI)

The leads connecting the instruments can pick up both magnet fields generated in all types of mains powered equipment from transformers, motors etc and RF interference from a mobile phone to a noisy switch mode power supply in a computer.

This produces great difficulties for high value (100Kohms) where impedance levels are high and test currents are low and every effort should be made to use screen leads which must be kept well away from sources of interference e.g. mains cables, computers, interface cables etc.

Note

To help reduce AC impedance the highest values of resistance in the 2000/3000 series calibrators have a 100pF capacitance across.

2.1.11.Note 7: Measuring resistance with AC.

Please note that this falls outside the scope of this procedure and has been included only for completeness Bridges often use AC to measure resistance, the resistors used in the 2000 series up to 100Kohms are of foil construction or non inductively wound and can be measured using AC up to 1kHz with little change in accuracy.

2.1.12.Uncertainties

See Spreadsheet

2.2.Scope - Automatic generation of 4 Wire Resistance from 0 to 10k.

2.2.1.Equipment

3000 Series CalibratorPrecision Low thermal Lead set

2.2.2.Connection diagram

2.2.3.Measurement Method:

1)Allow all equipment sufficient time to stabilise as per manufactures handbook.

2)Check environmental conditions e.g. mains voltage/frequency, temperature are within laboratories limits

3)Use a high insulation, low thermal screened lead and connect both the voltage sense leads, (to the top terminals) and the current drive leads the calibrator’s output to the measuring systems input. (see diagram above)

4)Connect guard and earth as required. (See notes below)

5)Select the zero ohms output from the calibrator and zero the measurement system

6)Set the output resistance required from the instruments calibration procedure. Turn output on. (For automated calibration ProCal will set the calibrator.) Refer to manufacture manual for equipment operation.

2.2.4. Important: Do not exceed the Maximum Power Rating

Care should be taken that the applied voltages and current do not exceed the calibrator’s specification. Do not connect insulation testers or ductors which test at high currents, exceeding the maximum ratings this will damage the resistor and change the resistance value.

2.2.5.Note 1: Errors due to thermals on low ohms.

Most resistance measuring instruments pass a DC current through the resistor and measure the voltage drop across it. For low values below 100 ohms and at low currents (10mA) often used by modern Digital multi meters makes the voltage to measure typically 100mV for 10ohms. A thermal generated EMF of 10uV in the test leads will give an error of 50ppM.

Many high performance DMM’s have an ohms compensation function to automatically null this out. This should be used to improve the reading. If such a function is not available great care should be taken to use low thermal test leads.

2.2.6.Note5: Nulling out measurement systems zero

Connect up sense and current wire to the calibrator, select zero ohms output on the calibrator and null the measurement system.

The 3000 series calibrators are calibrated for 4 wire ohms as the resistance relative to the zero position

2.2.7.Note 6: Errors due to Earthing and Guarding.

Earthing the resistance output can sometime introduce more noise on higher values in the reading as in some DMM’s the negative terminal in resistance mode is not the circuit low, but a current sink. Find the best connection by experimentally method. It may be best to connect earth to screen of the test leads and to the DMM’s guard, leaving the resistance measuring circuit to float.

The 3000 series calibrators can internally earth the low side of the output. The condition of this is shown on the display and by a green front panel LED.

2.2.8.Note 7: Errors due self heating and voltage coefficients

Measuring resistors at high power levels (above 0.5 watts) will cause the resistor to heat up, due to the temperature coefficient of the resistor the value will change. As the temperature rise reaches an equilibrium the value of resistance will also stabilise. When the power is removed the resistor will cool down and return to the original value. Generally the resistor should be measured at a power level, which will not cause self-heating, less than 10mW’s for example.

Voltage coefficient is the change in resistance with voltage, high value film type resistor values will normally reduce at high voltages - this effect is very small below 200Volts but may need to be considered above this. NOTE the resistors in the 3000 series maximum rating is 200V.

2.2.9.Note 8: Errors due Electromagnetic Interference (EMI)

The leads connecting the instruments can pick up both magnet fields generated in all types of mains powered equipment from transformers, motors etc and RF interference from a mobile phone to a noisy switch mode power supply in a computer.

This produces great difficulties for high value (100Kohms) where impedance levels are high and test currents are low and every effort should be made to use screen leads which must be kept well away from sources of interference e.g. mains leads, computers, interface leads etc.

Note

To help reduce AC impedance the highest values of resistance in the 3000 series calibrator have a 100pF capacitance across.

2.2.10.Note 9: Measuring resistance with AC.

Please note that this falls outside the scope of this procedure and has been included only for completeness Bridges often use AC to measure resistance, the resistors used in the 3000 series up to 100Kohms are of foil construction or non inductively wound and can be measured using AC up to 1kHz with little change in accuracy.

2.2.11.Uncertainties

See Spreadsheet

3.DC Current

3.1.Scope - Automatic generation of D.C. current in up to 2 Amps.

3.1.1.Equipment

3000 Series CalibratorPrecision Low thermal Lead set

3.1.2.Connection diagram

3.1.3.Measurement Method:

1)Allow all equipment sufficient time to stabilise as per manufactures handbook.

2)Check environmental conditions e.g. mains voltage/frequency, temperature are within laboratories limits

3)Use a 1 metre high insulation screened lead to connect the calibrator’s current output terminals to the input-measuring instrument under test. (See diagram above)

4)Connect guard and earth as required. (See note 1 below)

5)Check the Zero the measuring instrument and null if required.

6)Set the output current required from the instruments calibration procedure and turn output on (for automated calibration Procal will set the calibrator.)

7)Refer to manufacture manual for equipment operation.

3.1.4. Caution 1:

When using currents above 1 amp take care to ensure the measuring instrument is on the correct range and the correct input is being used.

3.1.5.Note 1: Calibrators Compliance (or burden) voltage exceeded

If the calibrator trips back into standby the calibrator’s output may be open circuit or the resistance to high to drive the set current.

3.1.6.Note 2: Errors due pick up and EMI interference when calibrating below 1mA

Accurate measurement of Currents below 100uA can easily become swamped out by stray magnetic fields & pick up. Unlike DC voltage where impedances are very low a current source has very high output impedance, which is therefore more susceptible to induced noise, making the use of screened leads essential for accurate measurements. Guards should be connected to earth and also the low side of the output.

3.2.Scope DC Current Source 2A to 30A

3.2.1.Equipment

3000 Series CalibratorPrecision Low thermal Lead set

3.2.2.Connection diagram

3.2.3.Measurement Method:

1)Allow all equipment sufficient time to stabilise as per manufactures handbook.

2)Check environmental conditions e.g. mains voltage/frequency, temperature are within laboratories limits

3)Use 30 Amp test leads to connect from the calibrator to the 30 Amp input terminals of the measuring instrument under test. Note high currents can melt low current test leads. (See diagram above)

4)Check the Zero of the measuring instrument and null if required.

5)Set the output current required from the instruments calibration procedure. Turn output on. (For automated calibration ProCal will set the calibrator.) Refer to manufacture manual for equipment operation.

3.2.4.Caution 1: