Ludlum 2401-S

Handheld survey meter

Ludlum 2401-S – handheld survey meter from Ludlum Measurements. Measurement range as specified: 0 to 50 µSv/h (0 to 5000 µR/hr). Weight as specified: 0.4 kg including battery.

Detector: 18 mm diameter CsI scintillation crystal (internal)1
Measurement range as specified: 0 to 50 µSv/h (0 to 5000 µR/hr)1
Weight as specified: 0.4 kg including battery1

Download product sheet (PDF)All values with references – for tender documents

Specifications checked against the manufacturer’s documents on 2026-10-16

Manufacturer’s product page (opens in a new tab)

Overview

Nuclear power & nuclear technology Defence, security & preparedness Emergency services & first response Environmental monitoring & radiation protection Industry & quality control

Specifications

The number after each value refers to the source listed below. Values are as published by the manufacturer; the exact configuration is always confirmed in our quotation.

Detector

Detector	18 mm diameter CsI scintillation crystal (internal)1

Measuring range

Measurement range as specified	0 to 50 µSv/h (0 to 5000 µR/hr)1
Sensitivity (¹³⁷Cs)	100 cpm per µR/hr2
Response time	Typically 5 s from 10 % to 90 % of final reading1
Energy response	Energy dependent1

Power & battery

Power supply	One 9 V battery2
Battery life and conditions	Typically 250 hours with alkaline battery1

Mechanical

Dimensions (H × W × L)	4.6 x 8.4 x 13.5 cm1
Weight as specified	0.4 kg including battery1

Environment & ratings

Operating temperature	−20 to +50 °C (−4 to 122 °F); may be certified for operation from −40 to +65 °C (−40 to 150 °F)3

The data comes from the manufacturer’s published documents. Manufacturers may change specifications; the current configuration and performance are confirmed in the quotation.

Documents

PDFModel 2401-S microR Pocket-Size Survey Meter (data sheet)Datasheet · Ludlum

Sources

The number after each value refers to the source listed below. Values are as published by the manufacturer; the exact configuration is always confirmed in our quotation.

1
Model 2401-S microR Pocket-Size Survey Meter
Publisher: Ludlum MeasurementsProduct page Specifications tab, 'Detector'; description; Specifications tab, 'Range'; Specifications tab, 'Battery Life'; Specifications tab, 'Size (H x W x L)' … Checked 2026-10-16
2
Model 2401-S microR Pocket-Size Survey Meter (data sheet)
Publisher: Ludlum MeasurementsDatasheet Specifications, 'Sensitivity'; Specifications, 'Power' Checked 2026-10-16
3
Ludlum Model 2401-S manual
Publisher: Ludlum MeasurementsManual Manual p. 13 (p. 5-1), section 5, Environmental Conditions for Normal Use Checked 2026-10-16