TECHNICAL NOTES - RT5

BB_hex, LSB₁, MSB₁, LSB₂, MSB₂, ...., LSB_N, MSB_N, BC_hex, BC_hex ,

where N is the number of digital channels.

A summary of the notation used follows -

 

T:   Updating period of signal values

C:   Chart speed, [in/sec]        (It is assumed that the host computer does not control chart motion).

N:   Number of (digital) channels

S:     Number of (resulting) samples per dotrow printed

th:	Time it takes the host to strobe-in the next byte, once the recorder  has gone from 'busy' to 'not-busy'. (Depends on host's software and hardware.)

tsc:  Time it takes the recorder to process one byte

tbp:  Time the recorders remains 'busy' while printing a dotrow

tbc:  Time to service a complete 'AVA' command

TA:   Time period between dotrows

In the case of t_sc, maximum and minimum values reflect its dependence on the relative timing between the external strobing of data, and the internal timing of tasks in the recorder.

If data is transmitted while the operator interface is in a state in which an item has been selected (for modification of the parameter itself or selection of the channel number, via the rotary control and/or Y/0, N/1 keys), the timing is altered very substantially:

t_{sc (while modifying)} = 2.9 ms
t_{bc (while modifying)} = 210 ms

Given the timing constraints above, let T_min denote the minimum updating period,
and F_max = 1/T_min. We have:
 

tbc = (2N + 3)(th + tsc)

(1)

Tmin = tbc + tbp= (2N + 3)(th + tsc) + 0.281N + 7   [ms]

(2)

With T_A denoting the time period between dotrows printed, we can also define the resulting number of samples per dotrow (S), as follows:
 

S = Fmax/FA [samples/dotrow],

(3)

where:
 

FA = 1/TA = C/0.01 [sec/dotrow]

(4)

C: chart speed in [in/sec].

The table below summarizes typical system performance for several configurations:

• Calculations use t_h = 0.25 ms, and t_sc = (0.17 + 0.45)/2 = 0.31 ms.
• Shadowed boxes indicate less than 1 sample/dotrow for the specified set-up.