Building on the success of the Mark 20, we have continued to improve the design with the Mark 26.  The most noticeable difference is the way the MK26 is mounted.  The MK26 is equipped with a solid copper mounting flange.  This new flange simplifies mounting and provides excellent thermal conductivity.  All TQCMs are designed to utilize a heatsink or mounting flange that will remain near ambient temperature.  A cable connector has been added to the rear for convenience.  An in-situ peltier and temperature sensor provide controllable heating and cooling capabilities to bring the temperature of the crystals to a temperature at which a gas of interest will condense on the crystal so that it can be measured.

The MK26 can be purchased with custom crystal frequencies to enhance mass measurements or sensitivity measurements down to the mono-molecular level.

The MK26 features a Peltier (thermoelectrically-controlled) heat exchanger which is used to raise or lower the temperature of the crystals.  This feature is useful for outgassing tests at low temperatures without supplying any refrigerant.  Also, by actively cooling the heat sink, the lowest temperature attainable by the crystal is further reduced.  The differential temperature that was available at ambient temperatures is reduced by the Joule heating effect, which cancels out the cooling capacity.

The MK26 has four design configurations:

• The MK26-1  is the standard unit, which utilizes the two-stage Peltier, operating at a temperature range of -60 °C to 80°C with 6.25 watts maximum power required for crystal temperature control, and has a customer selected option of 10 or 15 MHz crystal configuration.
• The MK26-2 Sub-Micron unit has similar temperature characteristics to the MK26-1, but uses mini-crystals, to enhance sensitivity over mass measurement.  The recommended customer selected crystal frequencies are 15, 25, and 50MHz.
• The MK26-3 Low Power unit With a single-stage Peltier, it has a slightly lower profile and measures only 0.722″ in height.  It has a temperature range of -38°C to 80°C with lower power requirements of 3.2 watts for crystal temperature control.  The -3 has recommended options of 10 or 15 MHz crystal frequencies.
• The MK26-4 Extended Frequency / Temperature Range utilizes a three-stage Peltier with a 4.4 watt maximum power requirement and an extended temperature range of -80°C to 80°C.  It uses the mini-crystals with recommended customer selected crystal frequencies of 15, 25, and 50MHz.

When used in a vacuum chamber, the MK26 TQCM is used with a QCM Research Model 2000 Control/Data Acquisition Unit.  The M2000 is able to handle up to twelve MK26 TQCMs at one time, and communicates with a host computer over an industry standard RS 232 serial link.

When used in flight, the MK26 TQCM is controlled with a QCM Research Model 3000 Flight Controller.  The M3000 is modular in design and can control two QCMs per module, with up four modules per M3000 providing eight QCM channels.