PTI, Photon Technology International, The Fluorescence Solutions Company

The Fluorescence Solutions Company



User Manuals  

Model 610/612/614 Photomultiplier Detection Systems








Inputs and Outputs

Modes of Operation



Attaching the Housing






The PTI Model 610, 612 and 614 detection systems consist of integrated photomultiplier tube (PMT) housings that include high voltage supply, controls and signal processing circuitry. All units feature a direct-read digital high voltage display. Various tubes are available to suit a variety of detection needs, and are easily installed within minutes.

Model 610 is a photon-counting (digital) type detector system with a built-in discriminator.

Model 612 is an analog type detector system with a built-in discriminator, and controls for gain, time constant, and offset.

Model 614 is a combined digital and analog detection system, with all of the electronics and controls of the 610 plus those of the 612. Detection/output mode of the 614 is set by an internal selector switch.

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All units have power on/off switch, high voltage adjust, LCD high voltage display, BNC signal output connection, BNC external high voltage adjust input connection, RF shielded case, and socket for most 1-1/8-inch side-on photomultiplier tubes. All models share the same internal high voltage power supply and come with a separate line voltage power supply.

High Voltage Power Supply - All Models

Input +/-15 VDC, 250 mA
High voltage -200 to -1,100 VDC manually adjustable
LCD display indicates actual cathode voltage or analog signal level
External high voltage adjust 0 to +5 VDC, continuously adjustable (0 = -200 V, 5 = -1,100 V)
Input regulation
+/-0.05% max. (for 15V +/-1V input)
Load regulation
+/-0.05% max.
100 mV p-p max.
Temperature coefficient
+/-0.01% max. (+5 to +40 deg. C)
Drift +/-0.03% / hr max. (after 15 minute warm-up)


Model 610/614 Photon-Counting (digital) Section

Maximum count rate
4 MHz
Pulse pair resolution
250 ns
TTL level active low pulse
Rise time 20 ns
Fall time 100 ns
Pulse width 220 ns


Model 612/614 Analog Section

Gain settings
1 µA = 1 V
0.1 µA = 1 V
0.01 µA = 1 V
0.001 µA = 1 V
Time constant settings
0.05 msec
0.5 msec
5 msec
50 msec
500 msec (0.5 sec)
Offset correction
+/-50 nA
Inherent noise 50 pA p-p typical, with 0.05 msec time constant



610 7.39 in. H x 4.04 in. W x 2.23 in. D
612/614 7.39 in. H x 4.04 in. W x 4.02 in. D


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Power ON/OFF - Both Models

Power ON/OFF controls the power supply to the PMT housing only. The analog section is always powered as long as the external (line) power supply is connected to it.

Voltage Adjust - Both Models

This dial adjusts the amplitude of the high voltage applied to the photocathode of the PMT. This voltage determines the gain of the PMT, and therefore the value of the output current from the PMT's anode caused by light incident on the photocathode. The voltage is adjustable from -200 to -1100 volts. When adjusting the voltage, care must be taken to prevent too much current from flowing in the PMT. Excessive current will cause vaporization of the anode and the destruction of the tube. The maximum current permissible is 10 microamperes (uA). The value of the high voltage can be seen on the LCD VOLTAGE display on the front of the PMT housing.

Mode Selector - Model 614 Only

The Mode Selector will have different effects on the signal output depending on the model. For the 610, the Mode Selector allows the user to choose between (processed) digital output and direct PMT output. For the 612, the Mode Selector allows the user to choose between (processed) analog output and direct PMT output. For the Model 614, the Mode Selector allows the user to choose between digital output, analog output, or direct PMT output. The cover of the main housing must be removed in order to gain access to the Mode Selector switch.

Gain - Models 612/614

Selects the electronic gain of the analog circuitry. Four gain settings are available:

1 µA = 1 Volt (x 1)
0.1 µA = 1 Volt (x 10-1)
0.01 µA = 1 Volt (x 10-2)
0.001 µA = 1 Volt (x 10-3)

Time Constant - Models 612/614

Selects the time constant of the filters in the analog circuitry. The choice of time constant affects both the noise filtering and the settling time of the output signal. A longer time constant will cause the output to be less noisy, but will increase the time necessary for the output to reach its final value. The settling time is approximately equal to five times the time constant.

Five time constant settings are available:

0.05 milliseconds (msec.)
0.5 msec.
5 msec.
50 msec.
500 msec. (.5 sec)

Offset - Models 612/614

Adjusts the amount that the output is offset from 0. This control can be used to eliminate the effects of dark current and other additive noise. The offset is adjustable +/-50 nanoamperes (nA).

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Inputs and Outputs

Power In

This input connects with a female 9-pin “D”connector from the power supply which carries the voltages and grounds necessary for proper operation of both the PMT housing and the optional analog circuitry. The voltages and connections are as follows:

  1. No Connection

  2. +15 Volts for High Voltage Supply

  3. -15 Volts for circuitry

  4. +15 Volts for circuitry

  5. NC

  6. NC

  7. HV Supply Ground

  8. Circuitry Ground

  9. NC

Ext. Volt. Control

This BNC connection accepts analog input from an external device such as a computer, allowing a control source for the high voltage other than the internal potentiometer of the PMT housing. The control source, either external or internal, is selected by a jumper on the printed circuit board inside the PMT housing. The lid must be removed to access this jumper. The external input voltage levels should be between 0 Volts for -200 Volts and +5 Volts for-1100 Volts.


This BNC connection provides the output to a measurement or display device, such as a computer, a recorder, or an oscilloscope.

Controls, Inputs and Outputs

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Modes of Operation

Model 610 operates in photon-counting (digital) mode or direct output mode. Model 612 operates in analog mode or direct output mode. Model 614 can be operated in digital, analog or direct output modes. Mode is controlled by the Mode Selector switch located inside the housing. The lid must be removed to access this switch.


This mode can be used for medium to high levels of light intensity. The maximum PMT current is 10 microamperes. The output is a DC signal between +13 Volts and –13 Volts. This signal is usually measured with a voltmeter, a recorder, or the analog-to-digital converter in a general-purpose I/O board in a computer.


This mode can be used for low to medium light levels up to 4 million counts per second. The output is a TTL level, active low signal. The signal line must be terminated at 50 ohms. The output is a frequency corresponding to the number of photons impinging upon the photocathode, and is usually measured with a counter in a general-purpose I/O board in a computer.

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Attaching the Housing

Remove the four screws from the housing cover and take the lid off the box. Verify the proper jumper settings. Using four flat-head machine screws, mount the housing onto the instrument. Plug the photomultiplier tube into the socket. Place the shroud over the tube. Check that all connectors for the cables that run from the PC board to the housing lid are secure. Replace the lid and close the housing tightly. Connect the power supply line and the signal cable(s).

NOTE: To ease insertion of the tube, orient the indexing pin so that the rib faces the back of the housing.

CAUTION: To avoid possible damage to the sensitive photomultiplier tube, it is suggested that the tube be kept in darkness as much as possible until it is installed in its socket and the housing is closed tightly.

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