YSI 556 MPS - Manual (Page 29)

Probe Module Section 3
YSI Incorporated YSI 556 MPS Page 23
8. Replace the probe sensor guard.
Dissolved Oxygen Sensor Installation
The YSI 5563 comes with the DO sensor already installed. Refer to Section
11.1.2 DO Sensor Replacement for instructions on installing the YSI 559
Replaceable DO Module Kit.
3.4.2 Membrane Cap Selection
The YSI 5563 is shipped with a YSI 5909 kit that contains membrane caps
made with 2 mil polyethylene (PE), a material which should be ideal for
most field applications of the 556. However, YSI also offers membrane caps
made with two other materials (1 mil polyethylene and 1 mil Teflon) which
some users may also prefer. All membranes available for the 556/5563
system provide comparable accuracy if used properly. The difference
between the two thicknesses of PE is found in the trade-off of flow
dependence and response time as described below. Teflon is offered because
some users may prefer to continue using the traditional membrane material
used by YSI. To avoid confusion, the membrane caps are color coded as
described below and can be ordered in kits as noted:
1 mil Teflon – Black Caps (Kit = YSI 5906)
1 mil Polyethylene (PE) – Yellow Caps (Kit = YSI 5908)
2 mil Polyethylene (PE) – Blue Caps (Kit = YSI 5909)
The 1 mil Teflon caps will offer traditional, reliable performance for most
dissolved oxygen applications. The 1 mil PE caps will provide a
significantly faster dissolved oxygen response (as long as your 556 Data
Filter is set correctly as described below in Sections 10.2 and 10.3.1) while
also giving readings which are significantly less flow dependent than the 1
mil Teflon caps. Finally, 2 mil PE caps will show a large reduction in flow
dependence over 1 mil Teflon while not significantly increasing the
response time. Generally, one of the PE caps is likely to provide better
performance for your application.
IMPORTANT: No matter which type of membrane cap you select, you
will have to confirm your selection in the 556 software from the Sensor
menu as described in Section 4 Sensors.