Status LEDs
The G478 utilizes three status LEDs.

The green LED varies intensity as the frequency changes from 0 to 100% of full scale range (e.g., for a configuration of 0-1000Hz, the LED will be off with an input of 0Hz and fully illuminated at 1000Hz. With an input of 500Hz, the LED will be dim). If the input signal is 10% more than full scale range (overranged), the LED will flash at 8Hz.

The yellow INPUT LED denotes input programming modes.

The red OUTPUT LED denotes output programming modes (see Configuration, Calibration and Figure 2 for details).

Configuration
Any 2Hz range from 0 to 10,000Hz can be converted to a full scale output signal (e.g. 0- 2Hz/4-20mA or 9998-10,000Hz/4-20mA).

Unless otherwise specified, the factory presets the Model G478 as follows:

Note: "Sensitivity" refers to the noise rejection level ( the trigger threshold) of the input.

For other I/O ranges, refer to Table 1 and 2. For calibration mode reference, see the stepby- step flow chart in Figure 4.

1. With DC power off, choose the desired output voltage/current range from Table 1 and set position 1 through 8 of SW1.
2. Set the Input sensitivity switch (SW1, 9 & 10) to LO for input amplitudes between 150mVp and 50Vrms, with noise rejection to 1Vp. Set the switch to HI for input amplitudes between 500mVp and 150Vrms, with noise rejection up to 10Vp (see Table 2).

1. Connect the input to a calibrated frequency source and apply power. Wait 1 hour for thermal stability before monitoring the voltage or current output.
2. Adjust the input frequency to the desired maximum and observe that the ouput has increased and is sensing the input. If the output does not increase, turn the sensitivity potentiometer in a counter-clockwise direction until the output begins to change proportionally to the input, plus another full turn.
3. Press the CAL button once to enter the calibration mode. The yellow and green LEDs will be on.
4. Input the maximum desired frequency and press the CAL button to store. The yellow LED will now be the only LED on.
5. Input the minimum desired frequency and press the CAL button to store. The green and red LEDs will now be on.
6. To precisely adjust the maximum output, adjust the input frequency until the output reads within +0.1% of the maximum selected output range. This typically occurs near 90% of the HI input frequency. Press the CAL button to store the value. The red LED will now be on.
7. To precisely adjust the minimum output, lower the input frequency until the output reads within +0.1% of the minimum selected ouput. This typically occurs near 10% of the HI input frequency. Press the CAL button to store the value. All three LEDs will be on.
8. Press the CAL button one final time to exit the calibration mode. The green LED will now be on.
9. Check the minimum and maximum input-tooutput calibration. Repeat steps 1 through 8 if calibration is not within desired specifications.

Optimal Sensitivity
If the amplitude of the input frequency is within the sensitivity parameters (i.e. 150mVp - 1Vp for LO and 0.5Vp - 10Vp for HI), then the sensitivity parameters can be set for optimum noise rejection:

1. Set the input near midrange (50% input) or to a frequency that exhibits the minimum pulse amplitude.
2. Turn the sensitivity pot (SENS) clockwise (CW) until the output drops to minimum.
3. Turn the sensitivity pot counterclockwise( CCW) a turn or two until the output returns to the previous level.
4. Run the input through the full frequency range to make sure that the pulses are sensed at both the low and high input frequencies. If the output drops out during this test (and the input freq. >0%) then turn the sensitivity pot counter-clockwise another turn or two until the output picks up. Repeat to validate sensitivity settings.