EPA Method 180.1 specifies criteria to use in determining an acceptable turbidimeter. These may be found in Section 5.4 of the method. Standard Method 2130 B specifies criteria to use in determining an acceptable turbidimeter. These may be found in Section 2.a of the method. The criteria specified are common to both methods and are listed below:

Light source: Tungsten lamp operated at a color temperature between 2200-3000 ^oK.

Distance traversed by incident light and scattered light within the sample tube: Total not to exceed 10 cm.

Detector: Centered at 90^o to the incident light path and not to exceed +/- 30^o from 90^o (e.g. between 60^o-120^o). The Detector and filter system, if used, shall have a spectral peak response between 400-600 nm.

In the Horiba Water Quality Checker U-10 the scattered light is measured at a point 30^o offset from the light source. This does not meet the detector requirements.

In the LaMotte Model 2008 the spectral peak response approached 900 nm. A letter from James O'Dell the ATP Coordinator for EPA states that the LaMotte Model 2008 does meet design criteria and is acceptable for compliance monitoring. Submittal of an Alternate Test Procedure (ATP) application is not required.