User Manual

ManualsBrandsAim TTi ManualsCycle CountersAim TTi TF930 Cycle counter 0.001 Hz - 3 GHz Manufacturer's standards (no certificate)

This setting should count most signals, but on very small signals some slight adjustment may be

needed for maximum sensitivity. The usable adjustment range from this position is approximately

±50mV (1:1 attenuation) or ±200mV (5:1 attenuation).

If DC coupling is in use then the feedback mechanism is disconnected and the threshold is

directly adjusted by the control over the range of nominally 0 to 2V (1:1 attenuation) or 0 to10V

(5:1 attenuation).

There is some over-range at each end of the control. The Threshold control should be adjusted in

the direction which brings both yellow LED lamps on and then finely adjusted to get the most

stable measurement.

For waveforms with slow edges adjusting the threshold will, of course, affect the Width and

associated Ratio and Duty cycle measurements but not Frequency, Period and Count.

The Threshold control should always be adjusted slowly, as there is a noise rejection filter with a

long time constant in the circuit.

Input B

Input B is used for frequency measurements in the range 80MHz to >3GHz. The input

impedance is nominally 50Ω. The maximum input voltage from 20MHz to 3GHz is 1Vrms and the

input is diode clipped with inputs over 250mVrms.

The input is protected against temporary accidental connection of mains voltages up to 250Vrms

at 50/60Hz.

The signal being measured should have a 50Ω source impedance to avoid standing waves which

could give spurious results. The input cable should be kept as short as possible and 50Ω coaxial

cable should be used.

Note that, because of the wide bandwidth of this input, signals mixed with other components

which fall within the frequency and sensitivity range of the input can cause incorrect counting;

externally attenuating or filtering the signal before presenting it to the counter may help to obtain

a correct reading. In particular, when attempting to count the highest frequency component of a

signal with broadband noise or other interference, an external high pass filter may be needed,

especially with small signals above 2GHz.

Function and Measurement Time Selection

Function and measurement time are selected using the keys immediately below the display. The

annunciators in the display show the current settings.

Function Selection – A input

Pressing the FREQUENCY, PERIOD or WIDTH key will immediately set the instrument to that

function; pressing and holding the key down for more than 1 second will change the function to

COUNT, RATIO or DUTY respectively, the 2

function printed above the key in blue; the selected

function is shown by the appropriate annunciator in the display.

FREQUENCY and PERIOD measurements are directly displayed in the appropriate units.

COUNT is a simple totalise function. The displayed value can be frozen with the HOLD key; the

count continues in the background. The count can be restarted (set to zero) using RESET, the 2

function of HOLD. When the count reaches the maximum of 9999999999, the next active edge

restarts the count from zero.

The WIDTH measurement can be set to measure either the High time (above the threshold) or

Low time (below the threshold) by choosing the appropriate polarity setting, see earlier Input A

Configuration Options section.

Selecting RATIO with the A input active shows the ratio of High time to Low time (RATIO H:L) or

vice-versa, according to the polarity setting. Low (inactive) time is calculated by subtracting the

measured High (active) time from the period.

Selecting DUTY shows the High time or Low time (depending on polarity setting) expressed as a

percentage of the total period.