Extech RPM33 Combination Mini Contact / Laser Photo Tachometer

Provides both contact (2 to 19,999 rpm) and non-contact (2 to 99,999 rpm) RPM measurements for enhanced versatility. Laser guided non-contact RPM measurements taken up to 1.6-foot (500mm) away for added safety.

Push-button Description

• MEM (Memory) button: Used to Record/Recall readings
• MEASURE button: Press and hold to take readings. The Laser pointer will switch on for Photo tachometer measurements when pressed
• MODE button: Press momentarily to switch measurement units. Press and hold for 2 seconds to switch between Surface Speed and Length measurement modes

Preparing for Measurements

Non-Contact (Photo) Tachometer Preparation

1. Apply a square piece of reflective tape to the surface of the object under test (nominal tape size: 0.5"/12mm). Be sure to affix the tape as close to the outer edge of the object under test as possible.
2. If not already done, unscrew and remove the meter collar (item number 3 in the Description section diagram)
3. Proceed to the "Taking Measurements" section below.

Contact Tachometer Preparation

1. If not already done, attach the collar (item number 3 in the Description section diagram) to the meter.
2. Slide the contact adaptor onto the tachometer's shaft. Be sure to align the adaptor with the alignment pin on the shaft of the contact adaptor.
3. Attach a contact measurement accessory (cone, wheel, or concave accessory) onto the contact adaptor.
4. For Contact operation the meter can measure Surface Speed or Length. Read the section titled "Surface Speed and Length Measurement Modes" later in this guide for details.
5. Follow the steps in the "Taking Measurements" section below.

Taking Measurements

Non-Contact (Photo) Tachometer Measurements

1. Prepare for the Non-Contact measurement as described in the Measurement Preparation section above.
2. Use the MODE button (momentarily presses) to select RPM (rotations per minute) or Hz (Hertz: rotations per second) as the unit of measure.
3. Press and hold the MEASURE button to begin a measurement session. Hold the MEASURE button down for the duration of the test and release it to end the session.
4. Point the meter toward the device under test at a distance of 2" to 20" (50 to 500mm). Be sure to align the laser light beam with the reflective tape (see diagram above in previous section).
5. Verify that the ((( ))) monitor indicator appears on the LCD when the reflective tape passes through the light beam.
6. Read the measurement result from the LCD display.
7. When the MEASURE button is released the last reading will remain on the display for 5 to 10 seconds before the `Auto Power OFF' feature switches the meter OFF. The HOLD display icon will switch ON.

Non-Contact (Photo tachometer) Measurement Considerations

• Bright ambient light may interfere with the reflected light beam. Shading the target area may be necessary in some cases.
• The non-reflective area must always be larger than the reflective area.
• If the shaft or rotating object is normally reflective, it must be covered with black tape or paint before the reflective tape is applied.
• To improve repeatability of low RPM measurements, apply additional squares of reflective tape. Divide the reading shown on the display by the number of pieces of reflective tape squares to calculate the actual RPM.

Contact Tachometer Measurements

1. Prepare for Contact measurements as described in the Measurement Preparation section above.
2. Determine if Surface Speed or Length measurements are to be made. Refer to the section "Surface Speed and Length Measurement Modes" later in this guide for details.
3. Press and hold the MEASURE button.
4. Touch the measurement accessory (cone, wheel, or concave accessory) to the object under test.
5. Read the measurement result from the LCD display.
6. When the Measure button is released the last reading will remain on the display for 5 to 10 seconds before the `Auto Power OFF' feature switches the meter OFF. The HOLD display icon will switch ON.
7. To change the unit of measure, first release the MEASURE button. Then, momentary presses of the MODE button will step through the available units. Refer to the Specifications section and to the section below entitled "Surface Speed and Length Measurement Modes" for units of measure details.

Surface Speed, Length, and Revolutions Measurement Modes

1. To switch between the Surface Speed and the Length measurement modes, press and hold the MODE button for two seconds.
2. The units of measure available in the Surface Speed mode are meters per minute (M/M), inches per minute (I/M), feet per minute (F/M), and yards per minute (Y/M). Step through the units selections with momentary presses of the MODE button.
3. The units of measure available in the Length measurement mode are meters (M), inches (I), feet (F), yards (Y), and revolutions (REV). The Revolutions (REV) mode is handy as a counter for use with custom sized wheel attachments to count (tally) wheel rotations. Step through the units selections with momentary presses of the MODE button.

Datalog Readings

The RPM33 can log up to ten (10) "reading sets" for each measurement session (for each unit of measure display). A reading set consists of four (4) values:

• Initial reading (reading recorded when MEM button is pressed)
• Maximum reading (MAX icon shown)
• Minimum reading (MIN icon shown)
• Average reading (AVG icon shown)

This totals 400 stored readings (4 values per reading set * 10 reading sets per measurement session * 10 units of measure displays)

A measurement session starts when the MEASURE button is pressed and ends when it is released. Logging starts when the user presses the MEM button momentarily and ends when the MEAUSURE button is released. The number shown on the LCD in the lower right hand corner (data 0 – 9) indicates the current memory location. See example time-line diagram below.

1. Press and hold the MEASURE button to begin a measurement session as described earlier.
2. While holding down the MEASURE button, press the MEM button momentarily. The reading on the display at the time of the MEM button press (initial reading) will be stored in the current reading set and the MIN/MAX/AVG tracking will begin. Note the reading set memory location on the lower right hand corner of the LCD.
3. The MIN/MAX/AVG readings are calculated over the course of the measurement session (starting from when the MEM button is pressed and ending when the MEASURE button is released). MIN/MAX/AVG readings are stored in the same reading set as the `initial reading'.
4. Release the MEASURE button to end the measurement session.
5. Now, momentary presses of the MEM button step through the initial reading, MAX, MIN, and AVG readings stored in the current memory location. Note that subsequent presses of the MEM button step through the remaining nine memory locations; be sure to note the memory location number when reviewing data to avoid confusion.
6. When recalling data, press and hold the MEM button to quickly jump from one reading set to another. The reading set number, on the lower right, scrolls while the MEM button is held.

Datalogging more than one Reading Set per Measurement Session

If the MEM button is pressed more than once during a measurement session, more than one reading set will be created for that measurement session (one reading set for each MEM press). This is useful if more than one `initial reading' is desired for a given measurement session. The MIN/MAX/AVG values logged in each reading set represent the MIN/MAX/AVG values recorded between the MEM presses.