Starrett SR200 User Manual

SR200 Surface Roughness Tester

User Manual

Table Of Contents

Chapter 1 Using the SR200 with a PC 3.3 Specification for Data Dump 5.5

Introduction to Surface Texture Printing 3.3 Chapter 6 Accessories 6.1

terminology and definitions 1.1 To cancel print: 3.3 Chapter 7 Maintenance 7.1

Surface Texture Definitions 1.1 Chapter 4 Menu Settings 4.1 Calibration 7.1

Parameter Definitions 1.2 Main Menu 4.1 Reference Standard 7.1

Ra 1.2 Cut off 4.1 Sensitivity Check and Adjustment 7.1

Rp 1.2 Evaluation length 4.1 Cleaning the Stylus 7.1

RSm 1.2 Parameters 4.1 Pick-up Skid 7.1

Rz 1.2 Range: 4.3

Rz1max 1.2 Range Selector Table 4.3

Rt 1.2 Print Settings: 4.3

Rmr 1.3 Units: 4.3

RPc 1.3 Filter: 4.3

Rsk 1.3 Dump Mode: 4.3

Rda 1.3 Dump Mode (Using your SR200

Chapter 2 Description 2.1 with a PC) 4.3

The Equipment 2.1 SPC Mode 4.4

Traverse Unit 2.2 Language Settings 4.4

Pick-up Mounting Components 2.3 Chapter 5 5.1

Mounting Bracket 2.3 Making Measurements

Adjustable Support 2.4 Technical Considerations 5.1

Pick-up holder 2.4 Operating Notes 5.1

Connector 2.4 On a horizontal surface 5.1

Pick-up 2.5 On other surfaces 5.1

Mounting 2.6 Cut off: 5.2

Chapter 3 Getting Started 3.1 Evaluation Length: 5.2

Battery 3.1 Table of Cut-off values 5.2

Connecting the Pick-up 3.1 Operating Error Indications 5.2

Making a measurement 3.2 Specification 5.3

Switching the SR200 ON 3.2 RS232 Output 5.3

To cancel a measurement 3.3 Printer Configuration 5.3

Chapter 1

Introduction to Surface Texture terminology and definitions

Surface Texture Definitions

Every components surface has some form of texture which varies according to its structure
and the way it has been manufactured. These surfaces can be broken down into three main
categories: Surface roughness, Waviness and Form. In order to predict a components behaviour
during use or to control the manufacturing process, it is necessary to quantify these surface
characteristics. This is done by using surface texture parameters.

Surface Texture Parameters: Can be separated into three basic types: Amplitude, Spacing
and Hybrid.

Amplitude Parameters: Measures of the vertical characteristics of the surface deviations.

Spacing Parameters: Measures of the horizontal characteristics of the surface deviations.

Hybrid Parameters: Combinations of spacing and amplitude parameters.

Mean Line: Is a least squares line of nominal form fitted through the primary profile where

the areas of the profile above and below this line are equal and kept to a minimum separation.
Profile filters as detailed in ISO11562 define the mean lines for the roughness and waviness
profiles.

Cut-off: A cut-off length (or sampling length) is a filter that uses either electronic (2CR)
or mathematical (Gaussian) means to remove or reduce unwanted data in order to look at
wavelengths in the region of interest.

Bandwidth: Is the ratio of the upper Cut-off (Lc) to the lower Cut-off (Ls).

Sample Length: The profile is divided into sample lengths l, which are long enough to include

a statistically reliable amount of data. For roughness and waviness analysis, the sample length
is equal to the selected cut-off (lc) wavelength. The sample length is also known as the cut-off
length.

Evaluation Length: The length in the direction of the X axis used for assessing the profile
under evaluation. The evaluation length may contain one or more sample lengths. For the
primary profiles the evaluation length is equal to the sample length.

1.1 SR200 Specifications subject to change

Note: almost all parameters are defined over one sample length, however in practice more than one sample
length is assessed (usually five) and the mean calculated. This provides a better statistical estimate of the

parameters measured value.

Parameter Definitions

Surface texture is quantified by parameters which relate to certain characteristics of the
texture. The SR200 offers the following parameters:

Ra, Rp, Rsm, Rz, Rt, Rmr, RPc, Rz1max, Rsk, Rda

Additional parameters can be analysed by downloading results to optional software.

Ra: Universally recognised, and most used, international parameter of roughness. It is the
arithmetic mean of the absolute departures of the roughness profile from the mean line.

Rp: Maximum profile peak height

Mathematically, the largest peak deviation of the roughness profile from the mean line within a
sampling length.

When more than one sampling length is analysed rp is the mean value of the individual rp
values for each sample.

RSm: The mean spacing between profile peaks at the mean line, measured within the
sampling length. (A profile peak is the highest point of the profile between an upwards and
downwards crossing of the mean line).

Rz: Rz = Rp + Rv and is the maximum peak to valley height of the profile within a sampling
length.

When more than one Sampling Length is analysed Rz is the mean value of the individual Rz
values for each Sampling Length.

Rz1max: Maximum Height of Profile

Highest peak to valley within a sampling length. When measured over several sampling lengths
the largest individual sampling length value is taken.

Also known in the past as Rymax, Ry, Rmax or Rti

Rt: Total Height of the Profile.

Maximum Peak to Valley Height of the Profile in the Assessment (evaluation) Length (ln).

SR200 Specifications subject to change 1.2

Rmr: Material Ratio is the length of bearing surface (expressed as a percentage of the
evaluation length ln) at a depth below the highest peak.

Replaces tp% - Bearing Ratio as defined in ISO 4287 - 1984

RPc: Peak Count

The number of local peaks which project through a selectable band centred about the mean line
or a line parallel to it. The count is determined only over the evaluation length though the results
are given in peaks per cm (or per inch)

Known as Pc before 1997

Rsk: Skewness

Rsk is a measure of the symmetry of the profile about the mean line.

This parameter indicates whether the spikes on the surface are predominately negative or
positive or if the profile has an even distribution of peaks and valleys.

Rda: R Delta a or Rda or RDa - Arithmetical Mean Slope

Arithmetical Mean Slope of the Profile within the Sampling Length.

1.3 SR200 Specifications subject to change

Chapter 2

Description

The SR200 is a portable, self-contained instrument for the

measurement of surface texture and is suitable for use in both the workshop and laboratory.
Parameters available for surface texture evaluation are:

Ra, Rz, Rt, Rp, Rmr, RPc, Rv, Rz1max, Rsk, Rda

An explanation of the surface texture parameters evaluated by this instrument is given in
Chapter 1.

The parameter evaluations and other functions of the instrument are microprocessor based.
The measurement results are displayed on an LCD screen and can be output to an optional
printer or computer for further evaluation.

The instrument is normally powered by an alkaline non-recharge-able battery. If preferred, an
optional power adaptor can be used

Figure 1

The Equipment

The standard SR200 includes:

• 1 Traverse unit

• 1 Standard Pickup

• 1 Reference Specimen

Note: certain items described in this handbook are optional and may not form part of your particular system.

SR200 Specifications subject to change 2.1

• 1 Pickup cable

• 1 Screwdriver

• 1 Battery

Traverse Unit

The top panel of the traverse unit carries a membrane type control panel and a liquid crystal
display. The unit houses the electronics for controlling the measurement sequence, computing
the mea-

surement data and outputting the results to the display, or to the

RS232 port for use with a printer (when included) or to a com-

puter, for further analysis.

The unit also contains a drive motor which traverses the pickup

across the surface to be measured. The measuring stroke always starts from the extreme
outward position. At the end of the measurement the pickup returns to this position ready for
the next

measurement. The traverse length is determined from selections of cut-off or length.

Figure 2

Pick-up
Connector Select Key Display

Measure key Scroll key Print key

Battery

Battery Compartment

RS232 Connector

2.2 SR200 Specifications subject to change

Pick-up Mounting Components

The pick-up is fastened to the drive shaft by the following means:

Mounting Bracket. This is clamped to the drive shaft by means of a knurled knob.

Although normally used upright, as shown in figure 3, it can be turned to angle the pick-up or to
take it off the centre line, as shown in figure 3a. It can also be mounted side-ways on the drive
shaft, when the right angle pick-up is in use.

Figure 3: pick up mounting

Insert Extension

Pick-up

rod here Clamp Drive Shaft

Connector Adjustable

Pick-up Support Mounting Bracket

Pick-up Holder

Use this mounting position when the right angled pick-up is used

Mounting Bracket
Clamp Screw

SR200 Specifications subject to change 2.3