Specifications

SR400 Specifications
5
SR400 SPECIFICATIONS
OVERVIEW
There are three complete counters identified as A,
B, and T. All counters count up to 200 MHz.
Counter A can count INPUT 1 or the 10 MHz
internal clock. Counter A is gated by AGATE, and
has a count capacity of 10
9
.
Counter B can count INPUT 1 or INPUT 2.
Counter B is gated by BGATE, has a count
capacity of 10
9
and may be used as the preset
counter to determine the count interval.
Counter T can count the internal 10 MHz clock,
INPUT 2, or the gate trigger. This counter may be
preset to determine the count period for up to 25
hours or 9 x 10
11
counts, gates, or triggers. The
timer has an accuracy or 25 ppm from 0 to 50∞C.
SIGNAL INPUTS
Bandwidth: dc to 300 MHz
Input impedance: 50 Ohms
Linear range: ± 300 mV (at input)
Input protection: ± 5 Vdc, 50 V for 1 µs
Overload recovery: 5 ns for <10 µs duration
overload
DISCRIMINATORS
Counters A, B, and T have independent
discriminators when counting the signal inputs.
All discriminator levels may be set to a fixed level
or scanned. A rear panel INHIBIT input (TTL
active high) can inhibit the discriminators to stop
the count.
Referenced to the signal inputs:
Discriminator range: -300 mV to +300 mV.
Discriminator slope: Rising or Falling
Resolution: 0.2 mV
Input offset voltage: 1 mV
Minimum pulse input: 10 mV
Pulse pair resolution: 5 ns.
DISC outputs: NIM levels into 50 Ohms
TRIGGER INPUT
Impedance: 10 KOhms
Threshold: ±2.000 Vdc in 1 mV steps
Slope: Rising or Falling
Protection: 15 Vdc, 100 V for 1 µs
GATE GENERATORS
There are two independent gates, AGATE and
BGATE, which enable the A and B counters. Both
gates are triggered by the TRIGGER input. The
gates may be fixed in time or scanned. The GATE
outputs show the positions of the gates with
respect to the discriminator outputs.
Insertion delay: 25 ns
Maximum delay: 999.2 ms
Minimum gate width: 5 ns
Maximum gate width: 999.2 ms or CW
Resolution: 0.1%, 1 ns minimum
Accuracy: 2 ns +1%
Jitter: 200 ps rms +100 ppm
Maximum trigger rate:1 MHz
GATE view outputs: NIM levels into 50 Ohms
GATE view error: < 2 ns
COUNTING MODES
A and B for a period determined by T preSET and
T input.
A ± B for a period determined by T preSET and T
input.
A for a period determined by B preSET and B
input.
SCAN AND DWELL
The number of count PERIODS or data points in a
scan may be set from 1 to 2000. The duration of
one count period is determined by the preset
condition.
The time between consecutive count periods is the
DWELL TIME and can be set from 2 ms to 60 s.
The DWELL output will be TTL high during the
DWELL time. This output can be used to trigger
external devices.
At the end of a scan (of 1 to 2000 count periods)
counting may be programmed to STOP or START
the scan over again.
The START key begins the first count period of
the programmed scan.