NEPTUNE Multifunction Professional Safety Multimeter

HT Instruments

Product Overview

The HT Instruments NEPTUNE is an orange and black handheld digital multimeter. Its front features a large LCD screen displaying measurements, a rotary selector dial for choosing functions (e.g., V, Ω, LoZ, OFF), and several push buttons for modes like MODE, ZERO, and HOLD. Input terminals are located at the bottom, labeled COM, VΩ/+, and Ω.

This document details the electrical specifications, general specifications, and reference guidelines for the NEPTUNE multimeter.

1. Electrical Specifications

Accuracy is calculated as [%reading + (num. dgt* resolution)] at 23°C ±5°, <80%RH.

DC Voltage (Autorange)

Range [V]	Resolution [V]	Accuracy	Input Impedance	Overload Protection
0.0 ÷ 999.9	0.1	±(0.5% reading + 2 digits)	5MΩ	1000VDC/ACrms

AC, AC+DC, LoZ TRMS Voltage (Autorange)

Range [V]	Resolution [V]	Frequency Range	Accuracy	Overload Protection
0.5 ÷ 999.9	0.1	32Hz ÷ 1kHz	±(0.5% reading + 2 digits)	1000VDC/ACrms

Input impedance VAC function: 5MΩ, Input impedance LoZ function: 3.5kΩ. Auto detection DC mode, Max crest factor: 1.5.

Voltage/Current Frequency (Autorange)

Range [Hz]	Resolution [Hz]	Accuracy
32.00 ÷ 99.99	0.01	±(0.1% reading + 1 digit)
100.0 ÷ 999.9	0.1	±(0.1% reading + 1 digit)

Voltage range: 0.5V ÷ 999V, Current range: 0.5A ÷ 3000A (Flex clamp F3000U), 1mV ÷ 1000mV (STD Clamp).

DC, AC, AC+DC Current (Standard Rigid Clamp + Flex Clamp FS=1V) – (Autorange)

Range [mV]	Resolution [mV]	Accuracy (*)
1 ÷ 1000	1	±(0.5% reading + 2 digits)

(*) For frequency >100Hz the accuracy is: ±(1.5% reading + 5 digits). Max crest factor: 3, Frequency bandwidth: 1kHz. Current zeroed for value <1%FS [A] (1V Flex clamp), Current zeroed for value <1%FS [A] (STD clamp).

AC TRMS Current (Flexible Clamp F3000U) – (Autorange)

Range [mV]	Resolution [mV]	Accuracy (*)
1 ÷ 3000	1	±(0.5% reading + 2 digits)

(*) For frequency >100Hz the accuracy is: ±(1.5% reading + 5 digits). Max crest factor: 3, Frequency bandwidth: 1kHz. Current zeroed for value <1%FS [A].

Inrush Current – DC, AC, AC+DC TRMS (Standard Rigid Clamp + Flex Clamp FS=1V)

Range [mV]	Resolution [mV]	Accuracy (*)
1 ÷ 1000	1	±(2% reading + 2 digits)

(*) Accuracy declared for frequency: DC, 42.5 ÷ 69Hz ; Max crest factor: 3; Sample frequency: 4kHz. Detection threshold: 1%FS [A] fixed. Response time: 1ms (Peak), 16.7ms, 20ms, 50ms, 100ms, 150ms, 175ms, 200ms (max RMS).

Inrush Current – AC TRMS (Flexible Clamp F3000U)

Range [mV]	Resolution [mV]	Accuracy (*)
1 ÷ 3000	1	±(2% reading + 2 digits)

Resistance and Continuity Test (Autorange)

Range [Ω]	Resolution [Ω]	Accuracy	Buzzer
0.0 ÷ 199.9	0.1	±(1.0% reading + 5 digits)	<30Ω
200 ÷ 1999	1	±(1.0% reading + 5 digits)	<30Ω

2. Harmonic Voltage and Current (Autorange)

Harmonic Order	Fundamental Frequency	Resolution	Accuracy (*) (not zeroed values)
DC	42.5Hz ÷ 69Hz	0.1V / 0.1A / 0.1%	±(5.0% reading + 20 digits)
1 ÷ 25		0.1V / 0.1A / 0.1%	±(5.0% reading + 10 digits)
THD%		0.1%	±(10.0% reading + 10 digits)

Accuracy of harmonics amplitudes expressed in % is evaluated considering the accuracy of parameters ratio.

(*) Harmonic voltages are zeroed in the followed conditions:

1° harmonic: value <0.5V
DC, 2° to 25° harmonics: harmonic value <0.5% fundamental value or value <0.5V

(*) Harmonic currents are zeroed in the followed conditions:

1° harmonic: value <1%FS[A]
DC, 2° to 25° harmonics: harmonic value <0.5% fundamental value or value <1%FS[A]

3. Insulation Resistance (MΩ)

Test Voltage [V]	Range [MΩ]	Resolution [MΩ]	Accuracy
50	0.01 ÷ 9.99	0.01	±(5.0% reading + 2 digits)
50	10.0 ÷ 99.9	0.1	±(2.0% reading + 2 digits)
100	0.01 ÷ 9.99	0.01	±(2.0% reading + 2 digits)
	10.0 ÷ 99.9	0.1	±(5.0% reading + 2 digits)
	100.0 ÷ 199.9	0.1	±(2.0% reading + 2 digits)
250	0.01 ÷ 9.99	0.01	±(5.0% reading + 2 digits)
	10.0 ÷ 99.9	0.1	±(2.0% reading + 2 digits)
	100 ÷ 499	1	±(5.0% reading + 2 digits)
500	0.01 ÷ 9.99	0.01	±(2.0% reading + 2 digits)
	10.0 ÷ 199.9	0.1	±(5.0% reading + 2 digits)
	200 ÷ 499	1	±(2.0% reading + 2 digits)
1000	0.01 ÷ 9.99	0.01	±(5.0% reading + 2 digits)
	10.0 ÷ 199.9	0.1	±(2.0% reading + 2 digits)
	200 ÷ 999	1	±(5.0% reading + 2 digits)
1000 ÷ 1999	1	±(5.0% reading + 2 digits)

Open voltage: nominal test voltage -0% +10%

Nominal test current: >1mA at 1kΩ x Vnom (50V, 100V, 250V, 1000V), >2.2mA at 230kΩ @ 500V

Short circuit current: <6.0mA for each test voltage

Safety protection: error message for input voltage> 10V

4. Continuity of Earth Conductors (LoΩ)

Range [Ω]	Resolution [Ω]	Accuracy
0.00 ÷ 9.99	0.01	±(2.0% reading + 2 digits)
10.0 ÷ 199.9	0.1	±(2.0% reading + 2 digits)

Test current: >200mA DC for R≤5Ω; DC Current resolution : 1mA, Accuracy: ±(5.0% reading + 5 digits)

Open voltage: 4V ≤ V₀ ≤ 12V

Safety protection: error message for input voltage> 10V

5. Phase Sequence Rotation with 1-Wire Method

Voltage Range [V]	Frequency Range
100.0 ÷ 999.9	42.5 ÷ 69Hz

(*) Measurement is only carried out by direct contact with metal live parts (not on insulation sheath).

6. General Specifications

Display

4 LCD, (max 9999 counts), sign, decimal point and bargraph
Automatic polarity indication
Backlight
Refresh frequency: 2/s
Conversion: TRMS

Features

Data HOLD
MAX/MIN
PEAK (Voltage and Current), response time = 1ms
Autorange
Automatic detection of AC/DC signals
Auto Power OFF after 15 minutes of idleness

Power Supply

4x1.5V alkaline batteries type AAA IEC LR03 ?
Battery life: V, A, Ω, approx 132h (backlight OFF); V, A, Ω, approx 68h (backlight ON); MΩ (@500V) approx 400 test (backlight OFF); LoΩ approx 2000 test (backlight OFF)

Mechanical Specifications

Dimensions (L x W x H): 175 x 85 x 55mm
Weight (included batteries): 420g
Mechanical protection: IP40

Environmental Conditions

Reference temperature: 23°C ± 5°C
Working temperature: 5°C ÷ 40°C
Working humidity: <80%RH
Storage temperature: -20°C ÷ 60°C
Storage humidity: <80%RH
Max height of use: 2000m

7. Reference Guidelines

Safety: IEC/EN61010-1, IEC/EN61010-2-030, IEC/EN61010-2-033
EMC: IEC/EN61326-1
Test MΩ: IEC/EN61557-2
Test LoΩ: IEC/EN61557-4
Phase sequence rotation: IEC/EN 61557-7
Insulation: double insulation
Pollution degree: 2
Category of measure: CAT IV 600V, CAT III 1000V to ground and between inputs

8. Compliance

This product conforms to the prescriptions of the European directive on low voltage 2014/35/EU and to EMC directive 2014/30/EU.

This product conforms to the prescriptions of the European directive 2011/65/EU (RoHS) and the European directive 2012/19/EU (WEEE).

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