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ac-s In-Situ Spectrophotometer

Based on the highly successful ac-9, the ac-spectra (ac-s) offers almost an order of magnitude increase in spectral resolution of in-situ absorption and beam attenuation. The 4 nm resolution allows for spectral "fingerprinting" and deconvolution analysis.

The ac-s features a proven flow-through system, compact size, and excellent stability. With 80 (+/-5) wavelength outputs from 400–730 nm, the 4 nm resolution allows for spectral “fingerprinting” and deconvolution analysis. The ac-s employs a 25-cm pathlength for effective measurement of the cleanest natural waters.


Diameter 10.4 cm
Length 79 cm
Weight in air 5.9 kg
Weight in water 0.8 kg


Input voltage 10–35 VDC
Output RS232, RS485
Current draw 0.83 A @ 12 V nominal
Connector MCBH6MP



Temperature range 0–30 o C
Depth rating 500 m


Spectral range 400–730 nm


Bandpass (FWHM), nm

400: 10–18
450: 10–16
550: 10–15
650: 10–18
730: 10–25
Pathlength, cm 10 or 25
Beam cross-section 8 mm dia. (nominal)
Linear dispersion 6–7.0 nm/mm
Resolution 4 nm
Precision, 400 to 449 nm +/-0.003 m-1 typ., 0.006 m-1 max @ 1 Hz
+/-0.005 m-1 typ., 0.012 m-1 max @ 4 Hz
Precision, 450 to 730 nm +/-0.0005 m-1 typ., 0.0015 m-1 max @ 1 Hz
+/-0.001 m-1 typ., 0.003 m-1 max @ 4 Hz
Accuracy 0.001–10 m-1


The list below includes (as applicable) the current product brochure, manual, and quick guide; software manual(s); and application notes.

Title Type Publication Date PDF File
ac-s Datasheet Product Datasheet Tuesday, August 22, 2017 PDF icon datasheet_acs.pdf
ac-s Drawing Product Drawing Tuesday, July 4, 2017 PDF icon drawing-ac-s.pdf
ac-s Frame Mounting Drawing Product Drawing Thursday, July 6, 2017 PDF icon drawing-ac-s-mounting-details.pdf
ac Meter Protocol Document Product Manual Thursday, July 6, 2017 PDF icon manual-acprotq.pdf
ac-s user manual Product Manual Tuesday, October 31, 2017 PDF icon acsm.pdf
Compass Host Software for acs/ac9 Meters Software Manual Thursday, July 6, 2017 PDF icon manual-compassb.pdf

WETView is a data acquisition and display program for acquiring and viewing the data produced by Sea-Bird's absorption and attenuation instruments; the ac-s and ACS-5000.

Version 7.1 released June 18, 2004
Package icon for Windows 7/8/10

Compass software provides a graphical user interface that allows you to configure, collect, view, and upload data from ac-s and ACS-500 spectrophotometers.

Version 2.01 released April 30, 2010
Package icon for Windows 7/8/10

The WET Labs Archive Processing program (WAP) provides primary processing of data files created by DH4 data handler and ac-s and ACS-5000 meters. This primary processing consists of extracting time-stamped raw data from the archive files and applying calibration coefficients to the data for all WET Labs instruments and selected instruments from other manufacturers.

Version 4.37 released March 3, 2015
File wap437.exe for Windows 7/8/10

What should I use to lubricate bulkhead connectors?

We recommend keeping the connectors on your meter lubricated using a good quality silicone spray lubricant, such as 3M Silicone Spray or Loctite 8021 spray. These can be purchased at your local hardware store. Avoid silicone grease. It is messy and attracts contaminants.

Do not use WD-40. It will destroy connectors.

What is the input voltage range for my instrument?