Technical Data
Fluke 1623 and 1625
GEO Earth Ground Testers
The new Fluke 1623 and 1625
GEO Earth Ground Testers offer
an innovative solution, called
Stakeless testing, to make your
earth ground loop resistance
testing quicker and easier. No
need for a separate earth
ground clamp.
• 3- and 4-pole Fall of Potential,
earth resistance loop testing
• 4-pole Soil Resistivity testing
• Selective earth ground rod
testing using 1 clamp
• Stakeless earth ground rod
testing using 2 clamps
• IP56 rated for outdoor use
• Rugged carrying case
In addition, the Fluke 1625 offers
these advanced features:
• Automatic Frequency Control
(AFC) - identifies existing
interference and chooses a
measurement frequency to
minimize its effect, providing
more accurate earth ground
value
• R* measurement - calculates
earth ground impedance at
55 Hz to more accurately
reflect the earth ground
resistance that a fault-to-
earth ground would see
• Adjustable limits - for quicker
testing
Stakeless testing
The Fluke 1623 and 1625 earth
ground testers are able to measure
earth ground loop resistances using
only clamps. With this test method,
two clamps are placed around the
earth ground rod and each are con-
nected to the tester. No earth ground
stakes are used at all. A known, fixed
voltage is induced by one clamp and
the current is measured using the
second clamp. Then the tester auto-
matically determines the resistance
of the earth ground rod.
This test method only works if a
bonded earth ground system exists for
the building or structure under test, but
most are. If there is only one path to
ground, like at many residential appli-
cations, the Stakeless method will not
provide an acceptable value and the Fall
of Potential test method must be used.
With Stakeless testing, the earth
ground rod does not need to be dis-
connected—leaving the bonded earth
ground system intact during test. Gone
are the days of spending time placing
and connecting stakes for each earth
ground rod on your system—a major
time saver. You can also perform earth
ground tests in places you’ve not
considered before: inside buildings,
power pylons, or anywhere you don’t
have access to soil.
2 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
General
Display:1999 digit LCD Display with special symbols, digit height 25 mm, fluorescent backlight
User interface Instant measurement through TURN and START one button concept. The only operating elements are
rotary switch and START button
Robust and waterproof Instrument is designed for tough environmental conditions (rubber protective cover, IP56)
Temperature ranges
Working temperature -10 °C to 50 °C (14 °F to 22 °F)
Operating temperature 0 °C to 35 °C (32 °F to 95 °F)
Storage temperature -20 °C to 60 °C (-4 °F to 140 °F)
Reference temperature 23 °C to ± 2 °C (73 °F to ± 4 °F)
The chart of four temperature ranges for the instrument exist to satisfy European Standards requirements; the instrument can be used over the full working
temperature range by using the temperature coefficient to calculate accuracy at the ambient temperature of use.
Temperature coefficient ± 0.1 % of reading/K
Intrinsic error Refers to the reference temperature range and is guaranteed for 1 year
Operating error Refers to the operating temperature range and is guaranteed for 1 year
Climatic class C1 (IEC 654-1), -5 °C to +45 °C (23° to +115° F), 5 % to 95 % RH
Protective type IP56 for case, IP40 for battery door according to EN60529
Safety Protection by double and/or reinforced insulation. max. 50 V to earth
EMC (Emission Immunity) IEC 61326-1:1997 Class A
Quality system Developed, designed and manufactured according to DIN ISO 9001
External voltage V ext, max = 24 V (dc, ac < 400 Hz), measurement inhibited for higher values
V ext rejection > 120 dB (162⁄3, 50, 60, 400 Hz)
Measuring time Typical 6 sec.
Max. overload 250 V rms (pertains to misuse)
Auxiliary power 6 x 1.5 V mignon cells alkali-manganese (type AA LR6)
Battery life span Typical > 3,000 measurements
Dimensions (WxHxD) 250 mm x 133 mm x 187 mm (9.75 in x 5.25 in x 7.35 in)
Weight 1.1 kg (2.43 lb) including batteries
1623 Specifications
The most complete testers
The Fluke 1623 and 1625 are distinctive earth
ground testers that can perform all four types of
earth ground measurement:
• 3- and 4-Pole Fall of Potential (using stakes)
• 4-Pole Soil Resistivity testing (using stakes)
• Selective testing (using 1 clamp and stakes)
• Stakeless testing (using 2 clamps only)
The testers are also easy to use. For each test,
the testers inform you which stakes or clamps need
to be connected and the large rotary switch can be
used even with a gloved hand.
The complete model kit comes with the 1623
or 1625 tester, test leads, 4 earth ground stakes,
3 cable reels with wire, 2 clamps, batteries, and
manual—all inside a rugged Fluke carrying case.
3 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
RA 3-pole ground resistance measurement (IEC 1557-5)
Switch position Resolution Measuring range Intrinsic error Operating error
RA 3-pole 0.001 Ω to 10 Ω0.001 Ω to 19.99 kΩ± (2 % rdg + 3 d) ± (5 % rdg + 3 d)
For 2-pole measurements connect terminals H and S with the supplied connector cable.
Measuring principle: Current and voltage measurement
Measuring voltage Vm = 48 V ac
Short-circuit current > 50 mA
Measure frequency 128 Hz (125 Hz on request)
Probe resistance (RS)Max 100 kΩ
Auxiliary earth electrode resistance (RH)Max. 100 kΩ
Additional error from RH and RSRH[kΩ]•••RS[kΩ]/RA[Ω]•••0.2 %
Monitoring of RS and RH with error indicator
Automatic range selection
Measurement is not performed if the current through the current clamp is too low
RA 4-pole ground resistance measurement (IEC 1557-5)
Switch position Resolution Measuring range Intrinsic error Operating error
RA 4-pole 0.001 Ω to 10 Ω0.001 Ω to 19.99 kΩ± (2 % rdg + 3 d) ± (5 % rdg + 3 d)
Measuring principle: Current/voltage measurement
Measuring voltage Vm = 48 V ac
Short-circuit current > 50 mA
Measuring frequency 128 Hz (125 Hz on request)
Probe resistance (RS+ RES)Max. 100 kΩ
Auxiliary earth electrode resistance (RH)Max. 100 kΩ
Additional error from RH and RSRH[kΩ]•••RS[kΩ/RA[Ω]•••0.2 %
Monitoring of RS, and RH with error indicator
Automatic range selection
RA 3-pole selective ground resistance measurement with current clamp (RA )
Switch position Resolution Measuring range Intrinsic error Operating error
RA 3-pole 0.001 Ω to 10 Ω0.001 Ω to 19.99 kΩ± (7 % rdg + 3 d) ± (10 % rdg + 5 d)
Measuring principle: Current/voltage measurement (with external current clamp)
Measuring voltage Vm = 48 V ac
Short-circuit current > 50 mA
Measuring frequency 128 Hz (125 Hz on request)
Probe resistance (RS)Max. 100 kΩ
Auxiliary earth electrode resistance (RH)Max. 100 kΩ
Monitoring of RS, and RH with error indicator
Automatic range selection
Measurement is not performed if the current through the current clamp is too low
4 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
RA 4-pole selective ground resistance measurement with current clamp (RA )
Switch position Resolution Measuring range Intrinsic error Operating error
RA 4-pole 0.001 Ω to 10 Ω0.001 Ω to 19.99 kΩ± (7 % rdg + 3 d) ± (10 % rdg + 5 d)
Measuring principle: Current/voltage measurement (with external current clamp)
Measuring voltage Vm = 48 V ac
Short-circuit current > 50 mA
Measuring frequency 128 Hz (125 Hz on request)
Probe resistance (RS)Max. 100 kΩ
Auxiliary earth electrode resistance (RH)Max. 100 kΩ
Monitoring of RS, and RH with error indicator
Automatic range selection
Measurement is not performed if the current through the current clamp is too low
Stakeless ground loop measurement ( )
Switch position Resolution Measuring range Intrinsic error Operating error
RA 4-pole 0.001 Ω to 0.1 Ω0.001 Ω to 199.9 Ω± (7 % rdg + 3 d) ± (10 % rdg + 5 d)
Measuring principle: Stakeless measurement of resistance in closed loops using two current transformers
Measuring voltage Vm = 48 V ac (primary)
Measuring frequency 128 Hz (125 Hz on request)
Noise current (IEXT)Max. IEXT = 10 A (ac) (RA < 20 Ω)
Max. IEXT = 2 A (ac) (RA > 20 Ω)
Automatic range selection
The information regarding stakeless ground loop measurements is only valid when used in conjunction with the recommended current clamps at the minimum
distance specified.
5 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
General
Description Microprocessor controlled, fully automated earth measuring instrument with additional functions
Measuring function Interference voltage and frequency, earthing resistance 3- and 4-pole with/without clip-on current transformer,
resistance 2-pole with ac, 2- and 4-pole with dc
Display 4 digit (2999 Digit) - 7 segment liquid crystal display, digit size 18 mm (0.71 in) with supplementary signs and
active illumination
Operation Central rotary switch and function keys
1625 Specifications
Temperature ranges
Working temperature range -10 °C to 50 °C (14° F to 122° F)
Operating temperature range 0 °C to 35 °C (32° F to 95° F)
Nominal temperature range 18 °C to 28 °C (64° F to 82° F)
Storage temperature range -30 °C to 60 °C (-22° F to 140° F)
Note: The chart of four temperature ranges for the instrument exist to satisfy European Standards requirements; the instrument can be used over the full Working
temperature range by using the temperature coefficient to calculate accuracy at the ambient temperature of use.
Temperature coefficient ± 0.1 % of range/Kelvin
Operating errors Refer to operating temperature range and RH < 20 RE, RS < 100 RE
The maximum percentage operating error within the measurement range does not exceed ± 30 % with the measured value as fiducial value, as determined in
accordance with Table 1 in the 1625 Users Manual.
The operating error applies under the rated operating conditions given in IEC1557-1 and the following:
• injection of series interference voltages with system frequencies of 400 Hz, 60 Hz, 50 Hz, 162/3 Hz or with dc voltage respectively across the terminals E (ES)
and S. The rms value of the series interference voltage shall be 3 V;
• resistance of the auxiliary earth electrode and of the probes: 0 to 100 x RA but ≤ 50 kΩ;
• system voltages between 85 % and 110 % of the nominal voltage and between 99 % and 101 % of the nominal system frequency for measuring equipment
with a mains supply and/or measuring equipment deriving its output voltage directly from the distribution system.
6 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
Limits of error Refer to nominal temperature range
Climate class C1 (IEC 654-1), -5 °C to 45 °C, 5 % to 95 % RH
Type of protection IP56 for case, IP40 for battery door according to EN60529
Max voltage
!
socket to socket
Urms = 0 V
Sockets ” “ to each other in any combination, max. Urms = 250 V (pertains to misuse)
EMC (Emission Immunity) IEC 61326-1:1997 Class A
Quality standard Developed, designed and manufactured to comply with DIN ISO 9001
External field influence Complies with DIN 43780 (8/76)
Auxiliary power 6 x 1.5 V alkali-manganese-batteries (IEC LR6 or type AA )
Battery life span With IEC LR6/type AA: typ. 3,000 measurements (RE+RH ≤ 1 kΩ)
With IEC LR6/type AA : typ. 6,000 measurements (RE + RH > 10 kΩ)
Dimensions (WxHxD) 250 mm x 133 mm x 187 mm (9.75 in x 5.25 in x 7.35 in)
Weight ≤ 1.1 kg (2.43 lb) without accessories
≤ 5.5 kg (12.13 lb) incl. accessories and batteries in carrying case
Case material NORYL, shock -and scratch proof thermoplast
Measurement of interference voltage dc + ac (UST)
Measuring Limits of error: method Fullwave rectification
Measuring Range Display Range Resolution Frequency Range Limits of Error
1 V to 50 V 0.0 V to 50 V 0.1 V dc/ac 45 Hz to 400 Hz sine ± (5 % of rdg + 5 digit)
Measuring sequence approx. 4 measurements/s
Internal resistance approx. 1.5 MΩ
Max. overload Urms = 250 V
Measurement of interference frequency (F )
Measuring method Measurement of oscillation period of the interference voltage
Measuring Range Display Range Resolution Range Limits of Error
6.0 Hz to 400 Hz 16.0 Hz to 299.9 Hz to 999 Hz 0.1 Hz to 1 Hz 1 V to 50 V ± (1 % of rdg + 2 digit)
Earthing resistance (RE)
Measuring method Current and voltage measurement with probe as IEC61557-5
Open circuit voltage 20/48 V, ac
Short circuit current 250 mA ac
Measuring frequency 94, 105, 111, 128 Hz selected manually or automatic. (AFC) 55 Hz in function R*
Noise rejection 120 dB (162/3, 50 , 60, 400 Hz)
Max. overload Urms = 250 V
7 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
Electrical measurement specifications
Intrinsic error or influence
quantity
Reference conditions or specified
operating range
Designation
code
Requirements or test in
accordance with the relevant
parts of IEC 1557
Type
of test
Intrinsic error Reference conditions A Part 5, 6.1 R
Position Reference position ± 90° E1 Part 1, 4.2 R
Supply voltage At the limits stated by the
manufacturer
E2 Part 1, 4.2, 4.3 R
Temperature 0 °C and 35 °C E3 Part 1, 4.2 T
Series interference voltage See 4.2 and 4.3 E4 Part 5, 4.2, 4.3 T
Resistance of the probes and
auxiliary earth electrodes
0 to 100 x RA but ≤ 50 kΩE5 Part 5, 4.3 T
System frequency 99 % to 101 % of the
nominal frequency
E7 Part 5, 4.3 T
System voltage 85 % to 110 % of the nominal voltage E8 Part 5, 4.3 T
Operating error Part 5, 4.3 R
A = intrinsic error
En = variations
R = routine test
T = type test
Measuring
Range Display Range Resolution Instrinsic Error Max. Operating Error
0.020 Ω to 0.001 Ω to 2.999 Ω0.001 Ω± ( 2 % of rdg + 2 digit ) ± ( 5 % of rdg + 5 digit )
300 kΩ3.00 Ω to 29.99 Ω0.01 Ω
30.0 Ω to 299.9 Ω0.1 Ω
0.300 kΩ to 2.999 kΩ1 Ω
3.00 kΩ to 29.99 kΩ10 Ω
30.0 kΩ to 299.9 kΩ100 Ω
Measuring time typ. 8 sec. with a fixed frequency
30 sec. max. with AFC and complete cycle of all measuring frequencies
Additional error because of probe-and auxiliary earth
electrode resistance
Measuring error of RH and RS typ. 10 % of RE + RS + RH
Max. probe resistance ≤ 1 MΩ
Max. auxiliary earth electrode resistance ≤ 1 MΩ
Automatic check if error is kept within the limits required by IEC61557-5.
If after a measurement of probe-, auxiliary earth electrode- and earthing resistance, a measurement error of higher than 30 % is assumed because of the influencing
conditions (see diagram), the display shows a warning symbol
!
and a notice that RS or RH are too high.
8 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
Automatic switchover of measuring resolution in
dependence to auxiliary earth electrode resistance RH
RH with Umeas = 48 V RH with Umeas = 20 V Resolution
< 300 Ω< 250 Ω1 mΩ
< 6 kΩ< 2.5 kΩ10 mΩ
< 60 kΩ< 25 kΩ100 mΩ
< 600 kΩ< 250 kΩ1 Ω
Selective measurement of the earthing
resistance (RE )
Measuring method Current and voltage measurement with
probe as per EN61557-5 and current
measurement in the individual branch
with additional current transformer
(patent applied for).
Open circuit voltage 20/48 V ac
Short circuit current 250 mA ac
Measuring frequency 94, 105, 111, 128 Hz selected manually
or automatically (AFC), 55 Hz (R*)
Noise rejection 120 dB (162/3, 50, 60, 400 Hz)
Max. overload Max. Urms = 250 V (measurement will
not be started)
Measuring Range Display range Resolution Intrinsic error* Operating error*
0.020 Ω to 30 kΩ0.001 to 2.999 Ω0.001 Ω± (7 % of rdg + 2 digit) ± (10 % of rdg + 5 digit)
3.00 to 29.99 Ω0.01 Ω
30.0 to 299.9 Ω0.1 Ω
0.300 to 2.999 kΩ1 Ω
3.00 to 29.99 kΩ10 Ω
* With recommended current clamps/transformers.
Additonal error because of probe- and auxiliary earth
typ. electrode resistance
Measuring error of RH and RSTyp. of 10 % of RETOTAL + RS + RH
Measuring time Typ. 8 sec. with a fixed frequency 30 sec. max. with AFC and complete cycle of
all measuring frequencies
Minimal current in single branch to be measured 0.5 mA With transformer (1000:1)
0.1 mA With transformer (200:1)
Max. interference current through transformer 3 A With a transformer (1000:1)
9 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
Resistance measurement (R~)
Measuring method Current and voltage measurement
Measuring voltage 20 V ac, square pulse
Short circuit current > 250 mA ac
Measuring frequency 94, 105, 111, 128 Hz selected manually or automatically (AFC)
Measuring range Display range Resolution Intrinsic error Operating errors
0.020 Ω to 300 kΩ0.001 Ω to 2.999 Ω0.001 Ω± (2 % of rdg + 2 digit) ± (5 % of rdg + 5 digit)
3.0 Ω to 29.99 Ω0.01 Ω
30 Ω to 299.9 Ω0.1 Ω
300 Ω to 2999 Ω1 Ω
3.0 kΩ to 29.99 kΩ10 Ω
30.0 kΩ to 299.9 kΩ100 Ω
Measuring time typ. 6 sec.
Max. interference voltage 24 V, with higher voltages measurement will not be started
Max overload Urms max. = 250 V
Resistance measurement (R )
Measuring method current- voltage measurement as per IEC61557-4 possible
Open circuit voltage 20 V dc
Short circuit current 200 mA dc
Formation of measured value with 4-pole measurement wires on H, S, ES can be extended without additional error.
Resistances > 1 Ω in wire E can cause additional error of 5m Ω/Ω.
Measuring range Display range Resolution Intrinsic error Operating error
0.020 Ω to 3 kΩ0.001 Ω to 2.999 Ω0.001 Ω± (2 % of rdg + 2 digit) ± (5 % of rdg + 5 digit)
3.0 Ω to 29.99 Ω0.01 Ω
30.0 Ω to 299.9 Ω0.1 Ω
300 Ω to 2999 Ω1 Ω
Measuring sequence Approx. 2 measurements/s
Measuring time Typ. 4 sec. incl. reversal of polarity (2-pole or 4-pole)
Max. interference voltage ≤ 3 V ac or dc, with higher voltages measurement will not be started
Max inductivity 2 Henry
Max. overload Urms = 250 V
Compensation of lead resistance (RK)
Compensation of lead resistance (RK) can be switched on in functions RE 3-pole, RE 4-pole , R~ , and R 2-pole
Formation of measured value Rdisplay = Rmeasured - Rcompensated*
* Value of setpoint entry RK = 0.000 Ω, variable from 0.000 to 29.99 Ω by means of measuring adjustment.
10 Fluke Corporation 1623 and 1625 GEO Earth Ground Testers
Ordering information
Fluke-1623 Kit Basic GEO Earth Ground Tester Kit
Fluke-1623 Basic GEO Earth Ground Tester
EI-1623 Selective/Stakeless Clamp Set for 1623
Fluke-1625 Kit Advanced GEO Earth Ground Tester Kit
Fluke-1625 Advanced GEO Earth Ground Tester
EI-1625 Selective/Stakeless Clamp Set for 1625
Optional accessories
ES-162P3 Stake Set for 3-Pole Measurement
ES-162P4 Stake Set for 4-Pole Measurement
Earth Stake Ground/Earth Stake
Cable-Reel 25 m Ground/Earth Cable Reel 25 m (81.25 ft)
Cable-Reel 50 m Ground/Earth Cable Reel 50 m (162.5 ft)
EI-162BN 320 mm (12.6 in) Split Core Transformer
Fluke Corporation
PO Box 9090, Everett, WA USA 98206
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
For more information call:
In the U.S.A. (800) 443-5853 or
Fax (425) 446-5116
In Europe/M-East/Africa +31 (0) 40 2675 200 or
Fax +31 (0) 40 2675 222
In Canada (800) 36-FLUKE or
Fax (905) 890-6866
From other countries +1 (425) 446-5500 or
Fax +1 (425) 446-5116
Web access: http://www.fluke.com
©2006 Fluke Corporation. All rights reserved.
Printed in U.S.A. 5/2006 2634980 D-EN-N Rev A
Fluke. Keeping your world
up and running.
Selection guide by user
Field Service
Technician
Industrial
Maintenance
Technician
Power Utilities
and Telecom
Fluke 1623 • •
Fluke 1625 • •
Standard earth ground test methods
Fall of Potential Selective Stakeless
3-pole 4-pole/soil 1 clamp 2 clamps
Fluke 1623 • • • •
Fluke 1625 • • • •
